bottom bracket problems, I think
Anytime I pedal hard - as in sprinting, or going up a hill, or whatever, I get a metallic, grinding, cranking noise. It happens in any gear, but it only happens on the drive side, when the pedal is at about 3:00 through 6:00. If I keep the pressure off the drive side, the noise mostly goes away.
I crashed in a race, but the bike fell on the non-drive side. The bottom bracket is only about two months (~1200 miles) old. Which, after having crashed, may mean nothing.
I was having this problem before the crash, and I took the bike in and the mechanics thought it was a bottom bracket issue. They took it out and regreased it. That seemed to solve the problem. But now, a few days later after the crash, the problem is back.
My bike's better than me!