Are you using a USB keyboard? If so, that is likely the cause of your problems.
Use a regular PS2 keyboard, and you should be fine.
If using a PS2 keyboard isnt working, then I'm not really sure what else the problem could be, and therefore wont know how to fix it.
The only other thing I can think of is a CMOS reset, which involves jumpers on the mobo. You can also do the same thing by taking the CMOS battery out for about 15 minutes.
Intel E6750...........PSN: ELBATROP
XFX nForce 650i Ultra
Patriot PC2-6400 8GB (4x2GB)
36GB WD Raptor
Samsung SyncMaster 931c
Samsung SyncMaster 750s
Windows 7 Home Premium 64