Confirmed on linux-3.0 rc5, 2.6.39.5 See mailing list for more information. The OOPS symbols are exactly the same in every instance. Booting 2.6.38.x repairs the filesystem and makes it mountable again with later versions. http://www.spinics.net/lists/linux-btrfs/msg10487.html
Closing, if this is still affecting you on a newer kernel please reopen.