Kubuntu 8.10 / Studio 15 / Switching display <=> vga output

Hi,
I'm running Kubuntu 8.10 on my new Studio 1537 with GMA X4500 HD built in. When I close the display, it switch off and the vga output is also deactivated. So there is no possibility to run the notebook connected to a TFT with closed display. I'm running a dual boot system and using vista this issue doesn't exist.

Have somebody a idea to solve the problem?

Thanks a lot!

Arthur