Cannot run avr-g++ (Create process error=5, Access is denied)

Actually, it's...

Cannot run "C:\Program Files (x86)\Arduino\hardware\tools\avr\bin\avr-g++": CreateProcess error=5, Access is denied"

This is what I get when I try to verify my code, which for the moment is one of the sample programs. I am running Windows 8 on a laptop. Uno is on COM7. This was working for a few days... now I get the error.

Any ideas? Do I need to set some permissions?