I´ve recently build the "Build your own PC 750$ edition" PC with 2 differences:
I reused my MasterCooler HAF Case and my old PSU and I have following problem:
When I connect my headphones (Sennheiser HD518) or my microphone (Logitech Desktop microphone) in the back audio-connectors of my mainboard I get clicking noises in my headphones and a rumbling noise on my microphone. When I connect them to the front ports of my case, there seems to be no problem at all. I already tried another sound device (speakers), and I don´t hear the clicking noises. Any ideas what could cause this?