hmm....maybe there is such a thing as "burn in" time...well, something like that...
When i first received my chip...i was able to hit higher fsb's too...and i was able to hit 1.69 (11.5x147)...and ran it stable for 2 days...then prime95 started giving me errors and i would also receive errors after playing counterstrike. Then, i heard of sickbeast who was running 1.7...now he's all the way back down to 1633. And now, i hear from you that you had to back down your OC too from what you had...
Just wondering cuz i saw this happen in some of the other systems i've built as well. But It could just be the fact that the artic silver and the cpu is very fresh and is giving lower temps and performing better and therefore gives more performence in terms of OCing...
enuf of my blabbling...