Strangely enough..
1) Start up in XP Home ...apps all launch fine
2) After awhile. some event happens on my computer behind the scenes ( may be linked to when browser fails to launch ...but I'm not sure at all)
3) Apps will not start -- double-click on shortcut or directly on *.exe icon, and hour glass shows for a few seconds as if app is launching, then...nothing happens, no app launch.
4) after restart, back to 1) again....everything launches fine.

Any ideas? Ad-aware and Spybot say the machine is completely clean...

Thanks

I have the exact same problem. It started a few days ago. When it happens, I can not open the task manager either, so I don't know if the processes are running. I can press ctrl-alt-del and get to "Windows Security"-screen, but when I press Task Manager, it just goes back to the desktop, shows hourglass for 5 seconds and nothing happens.
If I use Start > Run > taskmgr ... nothing happens.

Are the processes actually running?

Start > Run > taskmgr. See if Task Manager loads and check for the process(es).