I can confirm that an upgrade to edgy was enough to break my swap. The descibed procedure ("resume=uuid...") worked for me.
-- After running mkswap, swap space is discarded, system fails to hibernate (invalid swap signature) https://launchpad.net/bugs/66637 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs