Have you checked your derailleur hanger for straight? A crooked derailleur could cause the chain to be skippy. It looks like you needed to bend some things to get the brake bridge closer to the seat stay, and maybe the der hanger got tweeked in the process.
Last edited by cycle_maven; 08-20-09 at 12:48 PM.
Reason: D'oh. He said he tried new chain and cassette...