I noticed this as well. Usually I just shut the particular torrent down and restart it. Works fine after that, but it is still quite annoying. .68 seems to be a little buggy compared to the previous version, I've noticed a couple other things as well. Oh well, still the best client out there B) .
I was just tinkering with BitComet and I was wrong about the above. While it works sometimes, apparently the method doesn't always work :( .