Probably old news, but thought I'd point out that Kurt Stephens:
http://kurtstephens.com/node/148
thinks that this type of bug:
http://timetobleed.com/the-broken-promises-of-mrireeyarv/

is "is probably due to faulty register spilling" in the collector or
what not. Sorry I can't be of more help.  Also sorry if it's old news.
-roger-