Hello,sorry if i aou of topic but i hurry

Strange things happening with my Pegasos II

Recently i buy-et from Vesalia and using Voodoo5 pci without problems.
Ok,i want to change my videocar with Ati 7500LE/64 and i have problems
When i booting from CD the screen is ok,after i install MorphOS, de grafics come scrambled on my screen

I check the memory with another Pegasos II..OK
I check The video board with another Pegasos II ...OK
I run Gentoo live CD without problems with this board
it's something hidden in firmware?
I try 3 agp videocards and all have the same problems

Any hints?