Why without calling?
If your notebook model is supported for Linux you can call them but if not they will not help you at all.
Well I did it !
I was surprised that the person on the other side of the line tried to give me a solution. The solution was yours assex. A complete reinstallation of xp after switching to compatible mode, then reinstallation of ubuntu.
You must know at this stage that I have to do this for 11 other Toshiba nb200 (I'm a schoolteacher in a very small town of France and I do it for my children). So I don't think I will do this reinstallation (I didn't have the required CD anyway to reinstall xp !).
I will continue to boot Ubuntu by hitting some key several times after grub launching (found this fix here :
https://bugs.launchpad.net/ubuntu/+bug/577651), this was the way I had the best result for booting (about 30 seconds !). Maybe this will be fixed in a while. I hope so !
Thanks
Added link to fix