I had the same problem and I solved by reinstalling the gnome- screensaver package. Although it is now solved, I think this should be corrected for the next maintenance release of edgy. Unfortunately I couldn't find any trace of this problem in the log file for helping solving this problem.
-- Screen saver showing blank screen https://launchpad.net/bugs/65810 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
