I've been trying to figure this issue out for a while without luck so I'm hoping someone else has seen it.  After a PC reboot, my extender (DMA 2100) connects to my PC fine, but after a couple days it won't connect if the mediacenter has been awake for very long.  I have been able to pin it down to the "network location awareness" service.  If I restart the NLA service, or simply unplug/plug the PC interface the extender can connect and works fine.  This is the case until the computer sleeps/wakes again, after which the extender cannot find the PC again until I do the service restart or interface. 

 To make things more strange, if my PC has just been woken up, the extender connects fine.  It seems that there is a window of 5 or 10 minutes after the PC is awake that it will accept connections from an extender.

I am running Vista 64.  No strange error messages in the log which would indicate what the issue is.  I even did a fresh install a couple months ago, but as soon as I installed all the latest MS patches the issue came back.  I am running the Mediacenter standby tool and have another system that wakes (magic packet) the Mediacenter when the extender comes online. 

go to  the run command (windows key and R key) type secpol.msc ,  then hit enter.

 Then go to network list manager policies. Then set both uniddentifed and identified networks to Private. (right click properties). This should do it, but just to make sure then go to windows firewall advanced and under inbound rules, right click  add new rule,  predefined and select media extenders.

I promise us the firewall will never bother you again.

Robin

Thanks for the information, I didn't know there were policies for the Network List Manager so that is good information.  Unfortunately, that doesn't appear to be the problem and I still have the same issue. 

The only thing I can think of that I have different than anyone else is my mediacenter sleeps when not in use.  This worked great for a couple years and only started having issues 3-4 months ago. 

I am having the same issue. Tried this and it did not work. I have no problem with my wired DMA2100s. Just the single wireless one.

Mine turned out to be the NIC, which was the Atheros L1.  The really odd behavior followed me after installing Windows 7, so I replaced it with a $25 cheapo card as a test.  Problem solved.  I have the Atheros L1 POS built into two motherboards unfortunately. 

If its only the wireless giving you problems, you've pretty much narrowed it down to the wireless.  Make sure you are bridging wireless, not routing. The extender "tells" the mediacenter it is there using multicast packets.  Not all home routers support multicast and UPnP. 

I am having the same problem.  I can get it to reconnect if I reboot the router but only sometimes.  This happened after I upgraded my firmware for my DIR 855 router from dlink.  I am also using the new version of norton 360 that comcasts provides but I have set it to the settings that their help page suggests.  I have also tried the private network settings in the beginning but nothing is reliable. it seems that every so often it just gets a wild hair and will not connect so I have to fiddle around with things such as rebooting the router.  i would call dlink help but they are useless.

 Any suggestions would be appreciated.