BIOS refuses to match FSB freq with MEM freq

I just got a shuttle MN31N Mainboard that supports 333 FSB and an
Athlon Barton 2500+ that runs on the 333 FSB.

When booting the screen shows the Athlon at 1100mhz and memory at 333
mhz. Changing the FSB from 100 to 166 still shows the Athlon at 1100
and the memory shows speed at 200 MHZ and the system says it is in
safe mode and won't proceed. The only 2 memory adjustments that you
can make in the BIOS are [by Speed] or [Auto] and neither adjustment
will get the system to boot with the FSB at 166.

If I run the system at 100 FSB memory at 333MHZ it is very unstable,
getting to windows about 80% of the time but crashing when any program
tries to run.

Any suggestions?