Problem in configuring Xorg

[Bishal]

While trying to configure Xorg in freebsd 6.1 I get the following error.

  Failed to load module "speedo"
  No devices detected
  Fatal Server error:
  no screens found

 My display adapter is
        Driver      "sis"
        VendorName  "Silicon Integrated Systems [SiS]"
        BoardName   "SiS630 GUI Accelerator+3D"
        BusID       "PCI:1:0:0"


Earlier it was working fine with Freebsd 5.0 no when I did the fresh
install to freebsd 6.1 the graphical doesnot work.
Can anyone help me what's wrong with the xorg?

with best Regards
Bisal