x86-64 1280x1024 screen not displayed in the center

[blowek1]

So my problem is when I try to do 1280x1024 display resolution the top left of the desktop is about in the center and the bottom right is on the top right and there is blackness boardering it, it's like the display buffer has been shifted or something. This is a very important resolution since it is the native resolution of my LCD displays. However when I try in 1024x768 it seems ok. Also, when I enable Twinview the primary display still behaves as descrie above, but the secondary display is fine! I have tried may different configurations, and the config file use to work on my x86 system. I am running Redhat WS 3 X86-64 with kernel 2.4.21-15 and 2.4.21-15.0.4 smp and single processor with the same results. I have tried nvidia drivers 6111 and 6106 with simular results.

Hardware:
Dual Opteron
Tyan Tunder K8W s2885
Nvidia GeforeFX 5900 Ultra or Quadro4 900 GXL (at differnet times)

Any suggestions about hte problem will be helpful.
Thanks,
Brad

[blowek1]

On a side note, I have discovered something else odd about my system. I have 4GB of memory installed on the system. However, when I increace the size of the AGP appature the size that grub recognizes, then the kernel is decreased by a factor of approx. 2*appature. Anyone seen this before?

Brad