ATI Mobility Radeon x1400 driver problem Ubuntu 10.04

I am running Ubuntu on my laptop Toshiba A100-168 PSAAA9. There is a built in graphic card ATI Radeon Mobility X1400.
When I first installed it the graphic display stopped during the installation but I left it working. Then when the PC restarted Ubuntu run fine with high resolution. However 2 min after the display went unstable and the screen started to go black.
Here by using the remote desktop I tried to find solution to my problem by reading forums.
My first thought was to check the free driver was well installed. It was but actually was not appropriate to have a stable display.
Afterwards I tried to install the proprietary driver ATI 9.3 the latest from ATI to support my card. But unfortunately I couldn't as the Kernel of Ubuntu 10.04 do not allow me to run the installation properly.
So I tried to install the fglrx from the depot. And surprisingly after restarting I have got a stable graphic display in normal resolution. However I cannot use my the 3D effects of my graphic card.
I tried then to uninstall the free dirver radeon, I restarted and my PC with only fglrx is in very low resolution. No way to increase it. So I reinstalled radeon to have a stable environment and a normal resolution. I would like though to use my 3D capabilities.
I there a know solution to my problem: Why the free driver radeon do not allow me to have a stable graphic display; as it gets black after 2 min or less, should I set it up in a particular way...? Alternatively is there a way to install the proprietary driver 9.3 under Ubuntu 10.04?
Thanks for you help!