I have found that mates/mating seems to be a bit flakey/haywire in SW2k10.. is this true or is this just an inheritance from the person who worked on the assembly file before me? I change/add/delete a mate and I get a bunch of mate errors in other seemingly unrelated parts. I do a "control q"/rebuild and the mates seem to be fine again. I also get numerous times when the mate command gives me a "do you want Solidworks to prevent this" messages where Solidworks seems to helpfully make things worse. I am using SW2k10 SP4.0. I never noticed this "herky-jerky mate kabloohey" in previous versions, but then again I have not in the past been working on assemblies from this particular drafter either.