I haven't noticed that. But it is a constraint and with any of them
too many leads to over constrained parts. Maybe it was suppressed
in your 2010 model.
Have you checked the release notes?
I'm finding many slight differences in sketch that create over-constrained sketches. Many times I can delete a restraint or dimension, apply the same one again, and have no error. This is all with updated parts, so perhaps they didn't translate well. Nothing that slows me down too badly, so I'll just keep plugging.
We've had problems similar to yours since we started using SW back in the days of 98+. It looks like we can look forward to even more of them when we update to 2011 or, more likely, 2012. It always seems like the guys who write the code that checks stuff are more thorough than the guys who write the code that does stuff.