I've just built up a Planet X SL Pro Carbon jobbie as my new road bike. I've built quite a few mountain and road bikes over the years but never had this problem. It has a FSA Gossamer MegaExo compact crankset, 10 speed ultrega chain, 10 speed Ultegra Rear and front mech. I've adjusted the limit screws, b screw etc so that it should pedal nice and smoothly, but when I'm in the big ring front and little on the back there seems to be a cruching coming from the chainset or chain. I can't see that it's rubbing on the front mech, it seems to be where the chain is loading onto the chainset?
Sorry for the long post!