Mouse restricted to on Display in Xinerama mode


I succeed in setting up Xinerama mode in Catalyst Control Center by defining two separate displays and checking the Xinerama check mark.

The Problem is, that the mouse is restricted to on display.

On the DVI output there is a Panasonic TV with a resolution of 1920x1080 and on the analog output there is a Philips 200P with a resolution of 1600x1200 connected.

The video card is a Radeon 9800 XT with the proprietary driver fglrx version 9.3 installed.

Any idea?