Thanks for the responses guys!
Turning off the tv and turning it back on didn't do the trick. Unplugging it from the wall everytime he needs to switch inputs isn't too practical, especally since its a desktop computer. I'm hoping there is just a setting or something that needs to be changed.
From what I have posted, does it sound like there could be a problem with the videocard? Note that it works fine when not switchig inputs from the PS3.