Doesn't seem to work for me either on a Dell E1405 laptop (Core 1 Solo, Intel MB)...
mlweber@mattsbox:/$ openbox-logout
Suspending
Error org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 0
Failed
/usr/bin/openbox-logout: no process killed
Terminated
Simply running pm-suspend works just fine. It comes back with networking, video, and all working. Perhaps it has something to do with all of my "customizations". I will try again when I do a reinstall later, which I plan on doing as soon as the lite installer is ready (prod). The error message is the same for hibernate.