Sounds like your bike may have locked out the lowest gear? You may have been in a 39x25t while your buddy was in 39x27t. Check while riding to make sure you really are in your lowest gear. I know on some early alloy & carbon frames with standard-diameter tubing, the frame were really soft and auto-shifted into a higher gear when flexed uphill. Annoyed the heck out of me as I'd be struggling and not know why. Then I'd look down and find that it had shifted 1-2 gears higher.