Vista - windows alt+tab flipping lockup

has anyone had this problem? i will leave my computer with a few windows
open, walk away....10 minutes later it has a box in the middle as if i
pressed alt + tab that is flipping over the windows rapidly....the only way
out is to press the power button to force a shutdown....i don't know why it
is doing this... i do use a logitech g15 keyboard, but it does it with
others.... my overall windows score is 5.9, so i know my system is good....
also i thought i was out of blue screen hell, but it staryted again requiring
20+ boot attempts till it finally boots, or a windows restore....is that
caused by my radeon x1800? im using the lastest drivers....any info on these
2 issues please email me at johninabnit@comcast.net , this is killing
me...and i myself am a system developer