CF frame flexing?
Lately I've been hearing creaking sounds from the crank area of my Carbon fiber Argon Krypton. I just replaced the Truvativ crank with a Ultegra so I don't believe it to be a crank problem but perhaps just the sound of the frame when under strain from aggressive pedaling? Could it be a bearing issue?
This sound has been apparent with both cranks.
Sounds like the last change you made was with the cranks. You don't mention crashing, unusually severe chain drops, etc. Since something changed (you didn't have a creak and now you do), I'd look at any recent changes. In other words, I'd double check the crank installation.
Have an expert check the frame to see if you are getting too much flex...cranks not withstanding.