Yep, just more recent versions, and it's been fixed too. But if you watch the bugs that keep popping up for G1 you see stuff like this fairly regularly.

Of course, that's a totally unfair comparison: CMS has had a decade of bug squashing...I'm sure it had equally scary bugs when it was new. But that's the point. Don't use new, shiny GC's because they are still squishing bugs :)

(Sorry, preaching to the choir, I just get frustrated by everyone claiming G1 will solve all their problems without investigating potential downsides)