That's normal - Media Center only picks up the "major" channel, and generally not all the sub-channels available in a digital stream. Most PBS broadcasters are broadcasting multiple streams. Here, we get 3 "channels" from PBS...
Easy to add the additional channels - what's hard is to get Media Center to display the actual programming for PBS channels correctly (if at all...):
In Media Center -> Tasks -> Settings -> TV -> Guide -> Add Missing Channels -> Add DTV Channel. There it will give you two boxes to add the major channel number AND the subchannel number. Here you'll add one channel at a time. If you're adding "4.2" enter "4" in the first box (major channel and "2" in the second box (subchannel) and click OK. NEXT: You need to add the ACTUAL broadcast channel number here! If "4" in the analog channel number of the PBS station IT'S DIGITAL CHANNEL ASSIGNMENT will be different. (Here in Phoenix, PBS is "Channel 8" - that's where the analog broadcast is tuned. DIGITAL Channel 8 is actually broadcast on "Channel 29" (29.1 is their PBS HD Showcase, 29.2 is a digital broadcast of their "regular" (SDTV) PBS content, 29.3 is a 24-7 classical music broadcast...) So, if I add "8.2", I'm actually typing in 29 in the "assigned frequency" box. The next screen allows you to choose which "channel" (or broadcaster) to get the guide listing from - that's where this all sort of falls apart - you'll see...
If your analog provider is cable, chances are you have all the guide information you need, you just need to map it to the subchannels.
otherwise, its wait it out like the rest of us..
accident:The hack was actually designed for vista and your exact senario.. I ran into it during beta and saw a huge feature people wanted with a bigger problem when they got it.
Where can I find this hack? I have an antenna, an analogue, and two digital tuners. I'm concerned that the guide is going to tell my MC to record an hour of weather from 8.2 instead of an hour of HEROs on 8.1. I have only been up and running about a week so I haven't recorded much yet and haven't seen this issue, but it seems like a potential. Using a 360 as an extender.