I opened my G4 case to install a video card and now I can't close it. If I close it, the Power Mac beeps at me and the screen remains black. I don't know what could be the cause...it's the first time it ever does this to me. If I leave it about 30 or 25 degrees opened it works...but fully closed is no go. So right now I have it fully opened. Anyone ever encountered this problem?