I have Vista Ultimate x32. I also run Live OneCare constantly when the PC is running.
Lately, when I try to launch a number of different programs, they stop launching and I get a pop-up telling me that XXXXX (name of Program) has stopped working and that Windows is looking for the reason. It never finds anything. Subsequently, I cannot launch the program(s).
I ran a complete scan with Live OneCare and it advise the PC was clean.
What's happening???
Please advise.

There may be some clues in the "Report Problems and Solutions" in your control panel. Look at the failing module, type of error etc. that may be common amoungst your problems.

I have the same problem. The example I'll use is the game Fate by Wild Tangent. Here is a list of things I have tried to get it to run:

1. Run as Admin
2. Run in XP compatiblilty mode
3. Turned off DEP (Data Execution Prevention) for the Fate program
4. disabled Symantecs Antivirus
5. ran as a new user with all User protects turned off

The game ran fine on the computer out of the box, but after SP1 was installed, along with every other update that happens with a new computer, this problem started and I haven't been able to access it again.