I tried the 2.6.36 mainline kernel and suspend indeed works like a charm again (it even wakes up faster than with the standard Ubuntu kernel, but I already noticed this with lucid, too). Also, I checked the 2.6.35 mainline kernel: it had the same problems as the Ubuntu version, so it is definitely a problem with the kernel itself and not with Ubuntu's patches.
I tried the 2.6.36 mainline kernel and suspend indeed works like a charm again (it even wakes up faster than with the standard Ubuntu kernel, but I already noticed this with lucid, too). Also, I checked the 2.6.35 mainline kernel: it had the same problems as the Ubuntu version, so it is definitely a problem with the kernel itself and not with Ubuntu's patches.