Someone I know has a top of the line system, but whenever we try to play anything on 0.117/0.119 online, it skips/lags like crazy. If we switch to an older emulator like 0.64 or 0.61, the problem disappears immediately.
Since the problem is online, are you using the latest p2p dll? Makes online unplayable for me as well. Try using an older dll or different client dll? 
p2p client after 9/15 randomly enables recording even if you turn it off. It cuts the speed down to 75%. use 9/15 or older.
We’re using the Sept’ 15th client. I had this problem before when I installed 0.118 over 0.117, but I fixed it by re-installing MAME to another folder. This didn’t work for him though.
Then I’m almost certain he didn’t do it properly or …