What CPU is it. Some of the wolfdales that run with half multipliers dont display properly. For exampl i have an e7200 it runs at 2.53ghz with a 1066 fsb. So thats 266x9.5 for 2.53.
That chip is in a cheap foxconn board. By default the board always wants to run it at 266x9 for 2.4 or 133x9 for 1.2. The only way i have been able to solve this was to set the multiplier and FSB manully in the bios.
Ase Price suggested i would update the bios that may help. You might have to do what i did and just set the bios manually.
Another quick test you can do is to download coretemp. Its free it shows the temp and the frequency of the CPU. I would expect the chip to run at 266x6 for 1.6 while at idle. Then open a cpu heavy program the chip should ramp up to full speed.
Thermal monitoring can lower the FSB or the multiplier to avoide overheatings so also check the temps. If something is wrong with the heatsink and fan the chip might be dropping the fsb to control the heat.