I just completed a full overhaul and I find my chain skipping in middle gears. Overhaul included new cables, new housings, new chain, a lever overhaul (new G springs, return spring & coil spring), bottom bracket overhaul and hub overhaul. My LBS did the levers for me. I don't have bar tape on, yet. Housing is secured to bars with electrical tape (in several locations). I used old housing and old chain to determine correct lenghts. FYI I replaced my rear cassette last year with a new chain so I don't think the cassette is worn.
I followed Campy rear derailluer instructions to set limit screws and cable tension. I repeated this procedure several times after noticing the skip problerm. Cable tension feels good to me (not loose or super tight).
Before lever overhaul, I had shifting problems. It would miss shifts and I'd have to feather the lever a bit to complete some shifts. I didn't have a skipping problem.
I think this points to a lever problem, but I'm not sure. I'd appreciate any troubleshooting help.