When using the built-in window screenshot function on Ubuntu (alt-printscreen) with dual monitors, a black rectangle covers about the top third of the captured window (or that area is not captured). When capturing the entire screen (printscreen), the left monitor shows the same size rectangle, but it doesn't cover the window, but pushes it down. It's as if the capture is using the smaller monitor's dimensions, and is not aware of the larger monitor.

Here are the images:

Window capture: http://moby.to/8d69hp
Screen capture: http://moby.to/v99gqs

When using the command line, I get this error:

$ gnome-screenshot --window
(gnome-screenshot:8522): GdkPixbuf-CRITICAL **: gdk_pixbuf_composite: assertion `dest_y >= 0 && dest_y + dest_height <= dest->height' failed

System info:
Ubuntu 10.04.2 LTS (Lucid)
Linux 2.6.32-32-generic
Left monitor (laptop) 1280x800
Right monitor (external) 1920x1080

Is there a way to get this to work?

Edit: this does not happen with one monitor or when the monitors are mirrored.