Snag the older versions and see which one it happened in. If you pull out a 136 and it runs fast. Then do the same with a newer version and it runs slow it is not your computer. If you pull out a 136 and it runs slow something changed on your computer... Either way you can find out which version it happened in.
That should break the problem away from 'is it my computer or mame itself'. Which should help everyone diagnose what is going on.