As funny as this sounds, what type of shoes are you wearing? I know you mentioned your cleats but it could very much be the flexing of the sole on your shoes. It took me FOREVER to find where the god damn creaking was coming from on my bike and after doing everything, it came down the shoes I was wearing. Needless to say I used that as the first excuse to go out and buy a brand new pair. New shoes=no more squeeking and creaking. For me atleast!