I can confirm this on my system as well - I have a fresh Dapper Beta+updates install, and while sleep/hibernate work wonderfully from within Gnome and/or using the /etc/acpi/* scripts, selecting either option from GDM does nothing.
-- Suspend does nothing https://launchpad.net/bugs/3642 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
