After upgrading to 10.04 Lucid my PC will no longer resume from suspend. It suspends correctly, with the power light flashing, but on hitting the power button it goes straight into a full re-boot.

This was working fine in 9.04 & 9.10 (also in Windows), but now doesn't. I've tried 3 different graphics cards, as that's often a big part of the problem, but it's made no difference. The original card was Nvidia 5200, I've since swapped with a Matrox G550 and now an ATI Radeon. I've also tried s2ram, but there's no difference.

It's the same if I boot from the live CD, so there seems to be something fundamental that's changed in the way Lucid handles suspend.

Any ideas? I really hate having to shut-down and re-boot whenever I don't want to leave it on. I can't get hibernate to work either, but maybe that's another story.