all happened with no sign after i reboot my system

kde login screen change to black and white with a window at left bottom which writes console log for linux, and sometimes other information, there is no login button, you can only press enter to login

after login a xconsole window pop up automatically, which also writes console log for linux

besides after pressing logout button there is only end current session option,with restart and shutdown options missing.

all i have done before this happen is use Yast to update the nvidia drivers online

help me!

It somehow happened that you've changed your Display Manager from KDM to XDM.
Change it back!
(During installing the video drivers, there's supposed to be a question: what display manager do you want to use by default?)
What distro?
In debian, you do .

thanks a lot, the problem fixed