I had Adobe and Norton nagging me to reboot, so I did a normal reboot. After it came back up, a bunch of apps won't start:
The first one I noticed was Firefox. It would flash the disk light normally, but never appear on the screen. Then I tried to bring up an OpenOffice Calc window, same thing. I tried to bring up MS Word, and the splash screen appeared, but never the main screen, and the splash screen just sat there, with a swirly over it.
When I try to open up "Network and Sharing Center" the window appears, but nothing appears in it, and eventually it's tagged "not responding". When I kill that window I get (after a delay) "Windows Explorer is not responding", and when I say "OK" the screen resets.
But I tried Solitaire, Notepad++, Paint, and several others, and they popped up just fine. And I'm typing this from IE 8, which, if anything, came up faster than usual.
I tried rebooting again, and no joy — same problem as before.
Have done nothing particularly strange on this box, and it's not generally at significant risk for malware. I haven't installed anything new other than the afore-mentioned updates.
One other thing: Several minutes after rebooting I get the message "Error: Unable to start Bluetooth Stack Service." The Bluetooth radio is turned on, and I rarely have anything Bluetooth attached, and I don't recall that I've ever seen this message before.
Added: Looking at Event Viewer, I'm getting a lot of "The description for Event ID 1 from source xxx cannot be found." Is there any significance to this?
Added: I'm looking at restoring from backup, but the procedure is, at best, unclear. Is it sufficient to restore from "Backup and Restore Center", or must I restore from the restore DVD first?
A curiosity: Although it wasn't this way initially, the box has gotten to where it will not recognize USB devices (mouse or USB disk drive) if plugged in while the box is up. It does recognize them if booted with them in place, though.
Update: I'm currently restoring the system from recovery DVDs, and tracking it in How do I restore my system from a "Backup and Restore Center" backup?
Update: I'm having a similar problem again in my new question Firefox and Thunderbird won't start.