My bike has developed a nasty creak. It only shows up only when I'm either standing to climb (when it's pretty darn steep and I'm working hard) or when I'm standing to sprint or accelerate on the flats. Seems to happen once a pedal revolution, on the left. Doesn't happen when I'm seated, even in a big gear, pedaling hard. It's not a click, a squeak or a tick, it's a bad creak -- and I can actually feel it a little (but it's not a chain skip or something like that, it's coming from the cranks or the frame).

It sure sounds like it's coming from the bottom bracket, which I replaced two months ago. I'm neither terribly heavy (125) nor outrageously strong, and I haven't put on crazy mileage in that time, so I can't imagine I'd go through a bb that fast...

I checked the headset bolt, even though it doesn't seem to be coming from that part of the bike, and it was/is appropriately tightened.

I'm probably going to bring it in to the shop this weekend, but any ideas what I should be prepared for? (Please tell me I don't need a new bb again already...). Or if there's an easy fix I could do?

Thanks!!!!