I was having strange screensaver problems on my laptop as well, under Hardy as well as Jaunty. Recently I started having my problem again (not your problem...mine was the screensaver starting to come on then popping back out of it) and ran across the suggestion that I uninstall the Gnome Screensaver software and install xscreensaver (in the repos). So far it has worked perfectly.

What you have almost sounds more like a power managerment problem. Power management seems to come with the screensaver program (or perhaps it's just a GUI for the underlying power management daemon), so doing this might have a positive effect on your problem.

Something to try. The only time I close my laptop cover is when I turn it off and intend to move it. I don't use suspend or hibernate because I run BOINC distributed computing projects and the computer must be running at all times that I'm not transporting it.