Problem with PGX64

Hello
Got an strange problem with a PGX64 frame buffer, during bootup and in cli
mode everything
looks fine, but as soon as dtlogin starts and when i login everything looks
garbled ,chunks of graphic
pasted on different places on the screen. The machine is a Sunblade 150
running Solaris 8 2/02, the X server is run without any special options.
This machine got two PGX64 cards and when i switch to the other card
everything is fine. Has the frame buffer gone bad?

Thanks