When you cleaned with the compressed air, how far away was the bottle from the computer parts? if you hold the very edge of the jet of air to your hand and spray, see what happens. water will start to form in the palm of your hand. so if you got it too close to the computer when cleaning it out you could have created a tiny drop of moisture (or worse a big drop) and gotten it on something.
chances are you didn't, and maybe you just got something really cold that was runnning warm at the time (extreme temperature changes will effect overclock alot). If the air from the can was cold enough it could have messed with sumthin on your board and made it not so overclocking friendly. try burning in on stock settings for a while and heating the rig back up...then try overclockign again. i think that will solve your problem.
i never used compressed air for temperature reasons, and the small amount of condensation that forms if you get it too close or hold it over one spot too long. i just use a leaf bloser