I finally got my GD Viper working in 4X mode. There is a conflict between the 133A chipset and a number of boards (including early revisions of the Viper). I implemented the reg hack and it now boots and runs beautifully at 4X. I have confirmed this with wcpuid and Sandra. Quake II & III run at 1280 x 1024 with no problem. It took me so long to figure this out. Here's the reg hack :
[HKEY_LOCAL_MACHINE\Software\NVIDIA Corporation\Global\System]
"EnableVia4x"=dword:00000001
[HKEY_LOCAL_MACHINE\Software\NVIDIA Corporation\Global\System]
"EnableVia4x"=dword:00000001