There's a 'debugging weird noises' link over in the maintenance section of the forums, you might try that.

If your cleats (on you shoes) are adjustable, it could also be that.

I had (have, sometimes) a random squeek that is pedal / crank / cleat related - I stopped by the LBS and the mechanic
there gave me a quick list of 4-5 things to check to help isolate the issue.

and of course YMMV.