Comment 25 for bug 863834

In my case (Gnome3 on Oneiric on Thinkpad T60 with Radeon X1400) this is a collusion of two issues pointed out separately above:
(1) Gnome3's intended behavior is to disallow suspend while more than one monitor is active (comment #8, comment #3, [1])
(2) upower returns a false positive when asked whether more than one monitor is active (aka the is-docked state) for *some* graphic devices (comment #20, Bug #854404 and [2] is related but my false positive manifests on a system with a single video card)

Potential fix for issue (2) is in a patched upower package available at ppa:alexei.colin/upower (details on the patch are in [2]). Run 'upower -d | grep docked'. Note that because of a known issue with notifications [3] you might have to restart upowerd daemon to see the effect of turning off a screen; also note that the monitor must be cleanly turned off from display settings, pulling the cable doesn't change any state in my experience).

RANT:
(1) see upower rant in [2]
(2) This Gnome3 behavior should be configurable. Once issue (2) is fixed, the Gnome3's *intended* behavior is actually working, but that just creates the issue of how to get rid of this behavior... anybody know if it's configurable at least manually if not in Gnome GUI settings? (I'm not hopeful for more GUI settings after [4])

[1] http://blogs.gnome.org/hughsie/2011/02/02/is-gnome-3-going-to-melt-your-laptop/
[2] https://bugs.freedesktop.org/show_bug.cgi?id=36818
[3] From comment on PollDockDevices in UPower.conf: Poll the kernel for dock state changes. Some drivers are still broken, and do not send out uvents when the connected state changes. default=false
[4] http://afaikblog.wordpress.com/2011/02/03/on-laptop-lids-and-power-settings/