VESA BankSwitching under DPMI

Hi !
I had tried to program some VESA BankSwitching with the function $4F05 on
interrupt $10. Now it was me to slow and I coded it with the far call, whose
address I got from the function $4F01.
And it works. But under DPMI there is always a General protection fault. Of
course I got a Selector for the Segment.
Can anybody help me ?