I'm guessing your problems are different, since on my computer it won't even begin to suspend. The screen doesn't even go blank. It just pops up a message saying suspend failed and if gnome-screensaver is running it locks the screen.

I'm starting to wonder if the problem is just in some setting that I tweaked at some point and don't remember doing. Is there really no good way to find out what's preventing the machine from suspending?