Since you can't ride it, take out the post and inspect the 'scratch' to see how deep it really is. Find out the source and eliminate it. While the post is out, retighten the seat tube clamp. If the noise is still there, clean and lube the bolt and possibly the clamp (there may be dirt between the clamp and the frame. If it is silent, I'd inspect the area on the post where the seat tube clamp made contact a little closer.schimanski said:I certainly hope I haven't crushed it. It did sound awful but the noise is gone now (don't know if this is a good thing or not) and I even tightened it a bit more. There's no grinding/creaking sounds when I sit in the saddle, so I hope it didn't come from the post rather some dirt on the bolt or something like that. Too bad I can't test ride the bike for another month or two... ice and snow everywhere here.
If your bike has a separate clamp (not part of the frame but it slips over the seat tube, make ABSOLUTELY sure that this clamp is not touching the post when you tighten the bolt. This will be bad. There should always be a gap between the clamp and the post. I worked on a friend's bike not too long ago where the clamp was not all the way down on the seat tube and was overtightened - he had a nicely crimped post that needed to be replaced. With carbon the force would surely damage the post at least this much.