I installed the release version this morning, and the bug is back. I'm not sure what changed, as I was running an up-to-date dapper before the reinstall and it wasn't happening. Perhaps having also installed KDE and XFCE had something to do with it.
-- False reports of "Window not responding" error https://launchpad.net/bugs/29584 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs