I've seen video driver issues do similar, though "missing" the app has not usually part of that.
Now, for some questions:
1.) do you have Window Blinds?
2.) is Aero on?
3.) is Sidebar on?
4.) what video card and driver version?
5.) do you have the MS InteliPoint mouse driver installed?
1) Don't know what 'Window Blinds' are
2) Don't know what 'Aero' is
3) Sidebar is off (at least I don't see it)
4) NVidia GeForce 9600GS - but I have a Matrox MX02 Mini attached and have the same problem without it
5) Microsoft PS/2 Mouse
It's pretty much like a shooting gallery
I don't see how it would create your exact symptom, but it nothing else is fixing, consider a sticky key/failing keyboard.
I am clicking with Alt-Tab. Those keys work fine for everything else
I have a similar problem when pressing SHIFT with some symbols such as ( ) [ ] and +
There is a runaway autorepeat for as long as I keep the SHIFT key depressed, even though the symbol key has been released. This is on an Acer Vista laptop.
A colleage also had an Acer Vista laptop which exhibited the same behaviour, but nobody else seems to have this problem. I just assumed it was an obscure fault in the keyboard.