As with previous posts, again this is probably a local admin problem...
Technically no one is really a true administrator until all prompts and user
securitys are disabled in the security settings panel...
(start/run/secpol.msc/local policies/security options/scroll to bottom) and
then going into control panel and changing you account to an admistrator
manually. I initially thought i was an admin but your really only a local
admin by default. Go figure! Plus it gets rid of all those annoying pop up
warnings.
Also you can disable some of the little extras that you really dont need to
help with system performance. You can find info on this by clicking on the
link next to the system overall performance rating number and then the links
on how to improve your performance rating. And last but not least if you run
your vista cd... it has a repair option for just these types of problems...
it will just repair or attempt to repair whats not correct. Of course you
will probably have to do all the prompt disabling again but it may help. And
maybe set your pc to dump at startup. It kinda of sound like a memory
problem... but i really cant say for sure.