I have a PC with Windows XP SP3. Every once in a while, while using it, something weird would happen. The bottom half of the Start menu would be missing, everything from Programs down. When this happens, I cannot launch new applications or right click on any icons or files. Ctrl-alt-del would not do anything either. Any app that I have open would still work. The only way for me to get out of it is to hit the "reset" button to reboot my PC. Has anyone encountered this before? Could this be a virus or something XP related?