Depends on what chip you have and what motherboard you have. Could be the FSB isn't fully supported, and this is downclocked, or some power saving settings that force a lower multiplier on boot for whatever reason. Could also just be an incorrect BIOS reading. List your Specs. Also what speed does CPU-Z give you?
Yup, I forgot to mention that. You should download CPU-Z From CPUID.com and check what the real CPU ID is.