Vista - UAC is prompting on application start

UAC is prompting me every time I start FireFox. This just started happening
for no reason I can figure out. I've checked to make sure the shortcut isn't
set to "Run as administrator". I've re-installed FireFow it but that didn't
help. How can I correct this. It's annoying to have to confirm everytime I
run it. Also, the momentary flashing of the screen when it prompts also
sometimes changes the graphics back to Basic depending on what else I'm
running (like MovieMaker) at the time. Any suggestions?
Thanks
Doug