Rolling back the updates did not fix XM. Doing a system restore did not fix XM. Restoring a drive image from a couple of days ago, that fixed it but now I have another clue...
Adobe Flash Player... Yep. After the drive image restore I restored my data files which changed since the drive image. Outlook mailbox (pst), my financial data, iTunes, etc.
Testing XM, always worked. Then a popup on my screen said that adobe flash player needed an update. Actually, it said that there was an update available. I updated flash player, tested XM and it is broke AGAIN!.
I could not roll back the update so I just uninstalled flash player in the control panel. Launched Media Center, Music, More Music, XM Radio.
Now XM won't load at all. It seems that the XM menu uses Adobe Flash Player. On the screen was a link to click that would install / download flash player. Once the install started, a warning screen popped up saying that the software (Flash Player) was not written for Vista. I let it install anyway and wha-lah, XM works again.
This is nuts... Every time it breaks, I think I know the cause. Maybe this time I am right.
If anyone with this same problem has the guts, uninstall adobe flash player and re-install it. See if that fixes the XM app.
Edit: I was just on the adobe site. There is no official support for the flash player. There are all kinds of complaints about the player update breaking things. There are also several solutions in the forums.