I have a similar issue on my Thinkpad Edge 14 (Natty 32bit), when working in the Classic session.
Upon plugging in an external monitor [via HDMI], (or when booting with it plugged, after entering the session), the screen goes black (no mouse pointer either), with the external monitor picking no signal.
When unplugging, the laptop has a non-functional black screen with a mouse pointer.
I have a similar issue on my Thinkpad Edge 14 (Natty 32bit), when working in the Classic session.
Upon plugging in an external monitor [via HDMI], (or when booting with it plugged, after entering the session), the screen goes black (no mouse pointer either), with the external monitor picking no signal.
When unplugging, the laptop has a non-functional black screen with a mouse pointer.
The fix from [https:/ /launchpad. net/~bryce/ +archive/ elderberry] did not help.
[My symptoms match more closely those in duped #749817].