Throughout the boot, the login screen comes up as well as illustrates a few graphic problems (some slight horizontal lines, building the monitor look like scratched.

Choosing the user as well as login to Gnome work OK. The desktop shows graphic problems, also. After some seconds, Ubuntu will freeze. Only the mouse is still moving (sometimes with difficulties), but you cannot make use of it any longer (no click recognized), no key combinations seem to be recognized also. Neither memory nor CPU usage seem to be too high (looking at system monitor). System clock is not updated anymore; the freeze will not go away after some time. In the end, I have to switch off the PC to reboot.

This is a dual boot system, with the problem does not arise under "the other major operating system".

Workaround:

When I start Ubuntu into recovery mode as well as select "drop to root shell with network", followed by gdm start, I can make use of Gnome usually, the screen looks nice as well as fresh, no freeze will take place.

So I doubt what I could do to make it work as normal again? There must be an vital difference among normal mode as well as recovery mode + Gnome?

System: Dual boot Windows / Ubuntu 9.10 (Karmic)
ATI RV380 Radeon X600 (0x350) using radeon driver