Motherboard FSB and CPU FSB?

That will pose no problems. The CPU will run at it's maximum 800mhz as it isn't held back by the motherboard FSB frequency. If it was the otherway round and the CPU FSB frequency was 1333mhz and the motherboards was 800mhz then the cpu would be held back to 800mhz. But the answer to your question is that it will pose no problems.