OK here's the deal. I have a "media center PC" that I built a couple years ago in my living room.  It's running Vista home Premium and is connected to my ceiling mounted projector.  Only high speed internet available in my neighborhood is charter cable, so that's what I have for both TV and internet.  Using a Linksys BEFCMU10 (ver 3) cable modem and a cheapo Belkin FSD7230-4 (ve 1444) 802.11g router.  The router uses 192.168.2.1 and DHCP.  The router is "open," and the only "security" I use is MAC address filtering.  I made sure I added the MAC address for the DMA 2100, and have triple checked that it's correct and still there.  (I've also disabled the Vista firewall entirely)
I also have a 42" plasma in my bedroom that I've connected the DMA2100 extender to via HD-component jacks. I've tried the last 2 nights to set the extender up, and this is how it always goes:

Network Setup
I select "wireless network"

Choose your wireless Network -> Search complete
I select my network "Home 802.11g" (it usually sees 2-4 of my neighbors too)

Your player is being associated with the selected wireless network
Please wait

Address setting
How would you like to to obtain an IP address
If I select "automatically (recommended)" it moves on to

Currently searching for network configuration

then it says
"A network was not found
please make sure that your player is properly connected to your switch, hub or router.  Please refer to your user guide for troubleshooting."

then it dumps me back at Choose your wireless Network -> Search complete
where it again sees and I select my network "Home 802.11g" and the loop goes on.

If I change How would you like to to obtain an IP address
to "manually" and enter "192.168.2.10" as a static address, and list the routers address as 192.168.2.1 and 255.255.255.0.

This configuration tells me that the extender is set up, but when I go to get the set-up key it also tells me "A network was not found"

I have an "Airlink+" 802.11n router at work, and a "TrendNet" 802.11n router at work I  got to replace the "Airlink+" but haven't gotten around to yet, and I'm considering trying one or the other to see if it makes a diference, but really don't want to have to set up a new router, especially if that's not the problem.  I've also considered bringing home my 100' cat5 cable to temporarily connect the extender in a wired configuration, but the manual said that the DMA2100 stores wired and wireless settings seperately, so even if I get it up and running that way, it won't solve the wireless problem (and I can't leave the wire running down the hall and into the bedroom).

SO . . . . anyone have any suggestions? Please :(
(If I can't get this thing to work soon I'll need to send it back)

I never got my 2100 to work with my D-Link N router.  I read somewhere here it has problems with the wireless chip from Atheros in the router.  Searching on this site, you'll find more references to this issue and some possible workarounds.  In my case, I wired my 2100 and I believe this is always the better way to go if possible. 

Danno100:

I never got my 2100 to work with my D-Link N router.  I read somewhere here it has problems with the wireless chip from Atheros in the router.  Searching on this site, you'll find more references to this issue and some possible workarounds.  In my case, I wired my 2100 and I believe this is always the better way to go if possible. 

I got this BECAUSE of the wireless feature.  If I have to run a permanent wire to get it to work, I'll send it back!
I was thinking that worst case I'd have to upgrade my home router to a Linksys 802.11n one.  That would kind of kill the deal I got on the extender though, and I don't know why that should be NECESSARY. 
Really still looking for a solution to work with some of my existing equipment.

I couldn't get it to work (over Wireless G) either, I luckily had a Wireless G game extender (goes from wireless G to ethernet) and that worked.

I switched to Homeplug A/V now, so alls good (but that was another investment)

Do you have the HTPC connected to the router by "hard wire"? You can't have a wireless connection to the router and a wireless connection to the DMA2100. If you do, test up setup by hardwiring the HTPC to the router then rerun the DMA setup.

CountryBumkin:

Do you have the HTPC connected to the router by "hard wire"? You can't have a wireless connection to the router and a wireless connection to the DMA2100. If you do, test up setup by hardwiring the HTPC to the router then rerun the DMA setup.

Yeah the only thing connected by "hard wire" to the router is the cable modem, the HTPC and the MyBookWorldEd NAS. 
I'm going to bring home my 100' network cable tonight, and one of the 802.11n routers here in my office and see if either a wired set up, or a faster/different router makes a difference I guess.

baldbear:

I couldn't get it to work (over Wireless G) either, I luckily had a Wireless G game extender (goes from wireless G to ethernet) and that worked. I switched to Homeplug A/V now, so alls good (but that was another investment)

Wireless G game extender?  Is that the same as a range extender? How did that work?
I'd be concerned that with most range extenders lose your duplexing ability and if I'm already trying to stream over a G connection that might be asking for trouble, but maybe you found differently. 
I'd love to hear more about your experience.

Whooo Hooo!
I brought home a cable and N router.
Ran the cable back 1st and it worked!
So then I start changing settings and accidentally changed resolution from 1080i to 1080p and the whole thing goes black - no signal.
Switch the component input to HDMI, and it comes back.  Then I changed it back to 1080i and component input.  Finally I try to change the network from wired to wireless and still nothing, so i reset the wired and update the firmware.  Try everything again, still no wireless.
Last I switched the Belkin G router for the Airlink+ N router.  Suddenly  I was able to change the network from wired to wireless and IT WORKED.  Disconnected the wire, and I'm watching an episode of "House" I recorded months ago, while I'm in bed.
So I guess the moral of the story is don't try a wireless connection unless it's N.

I just received my 2100 today after ordering it on Wed! ($105-Amazon) 

I got it for the same reason. To have wireless access in the Bedroom (Upstairs).

I initially set it up downstairs in the HT Room so that I can access the HTPC & 2100 at the same time. I connected the ethernet 1st as to have direct, quick access for updates and network settings.

All went well except for the fact that I use a WPA-PSK AND A filtered MAC Address list. (WRT54G)

Everything runs fine except when I enter the MAC Address to the allowed list. The 2100 does not connect. I quad checked the Address and the list but it will only work with the filtered list turned off.

When it's on I get the same error MDEnce gets:

"No Network Found"

While my network is secure I like having control of which MAC Addresses are allowed. It's annoying but other than that this is nice.

Anyone else have this issue?

On my 2100, the mac address(s) are completely different than stated on the label. & the box. The box was sealed and the serial numbers match.

I turned off MAC filtering and checked on the client list of the router to get the correct wireless mac.

I still can not get WEP working. I have a couple of older devices that only support WEP.

I have a DMA 2200.  I used a ethernet over power line adapter and it works great.  That saves you the hassle of dealing with the wireless situation.  I got it up and running in around 10 minutes.  Granted having the wireless feature would be ideal but this way it is hard wired and you don't need to deal with router settings or going through a tedious set up to get the wireless to work if you encounter problems.

Ended up getting it working.

Ironically we had a Power outage and when I got back home I re-did a quicksetup and when I went into my network settings for the manual config there was a different MAC ADDRESS there.

I then added the new address to the list and whaddaya know. Turns out then that the 1st MAC/the Matching MAC on the Bottom is wrong!

Talk about causing a network issue.

So as it stands it's working with my MAC filter list and my WPA PSK. All is good.

For the record, I've had many networking issues while trying to use WEP so I stay away from it and go the PSK route. I suggest you do the same if you can.

I just experienced the same thing.   MAC address on box and DMA2100 label match each other, but are incorrect.  I had to turn off MAC address filtering to find the real MAC address.  The DMA2100 works great.  Seems like a manufacturing issue with the labeling.

SpencerF:

I just experienced the same thing.   MAC address on box and DMA2100 label match each other, but are incorrect.  I had to turn off MAC address filtering to find the real MAC address.  The DMA2100 works great.  Seems like a manufacturing issue with the labeling.

Either that or we got a bunch of refurbed/repackaged boxes.

Which of course would be illegal if the product was labeled and bought "new".

Not a big enough deal for me as everything is working. Only other issue I've had (Not really an issue) is that I've tried the box on a few different sets and noticed that when connected via component it takes about 45 seconds to boot but on HDMI it's a quick 5-10 sec....

Other than that, it's been great.

Royal Tee:

Only other issue I've had (Not really an issue) is that I've tried the box on a few different sets and noticed that when connected via component it takes about 45 seconds to boot but on HDMI it's a quick 5-10 sec....

That's odd! My DMA's take over a minute to boot, and they're connected via HDMI.