Well the chainset and cassette are different sizes to before (shifting was fine before also) - But you may be in to something in that the new chain may be too long. Thinking about it, I also get a little slippage in the 11 tooth in the big ring, which backs up this idea...
I take it that the chain you replaced was the same length as the one you removed?
Sheldon says:
Full-link overlap, correct
with chain on the large chain-
wheel and sprocket but not yet
run through the rear derailer