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I have a problem when trying to login to my Kubuntu 10.10. The login screen shows up, then I type my password, a blank screen is shown with my desktop background picture and then throws me back on the login screen.

if I choose to login from console, I can do that, and by typing startx I can log in just fine but in the end I cannot shutdown the computer from the k menu nor will my settings remembered for the next time I log back.

I have my home directory mounted from a different partition but I tried to create a new user account and I could log in without any kind of problem.

The home directory is not encrypted, at least not to my knowledge.

Some log files:

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Can you post the output dmesg and the contents of /var/log/Xorg.0.log and /var/log/kdm.log? – Lekensteyn Feb 19 '11 at 16:02
thanks for the response. can you see something from the log files? – Balázs Mária Németh Feb 19 '11 at 17:44
Nothing abnormal in those error logs. Can you post the contents of ~/.xsession-errors? Does the problem persist between boots? Have you recentely (un)installed software? When I removed the properietary nVIDIA driver, I had to reinstall the graphics driver libgl1-mesa-glx. – Lekensteyn Feb 19 '11 at 20:51
added the xsession errors as well. i had the problem for about 2 weeks, so i don't remember exactly, but i played around with reinstalling the graphic driver. – Balázs Mária Németh Feb 20 '11 at 13:59
i installed xfce to find out if i can login normally by an other desktop manager so i can find out if the problem lies with the mounted home dir. and i could login just fine. after that - i do not have any clue how - i could also normally login by kde. so there must have been some wrong configuration in my user account or some buggy package (i can only remember this removed: libgd2-noxpm) what was removed during the install of xfce. now i removed xfce and i have kde only, and everything runs smoothly. would not be bad to identify the cause of the problem though. – Balázs Mária Németh Feb 20 '11 at 15:16

In dmesg towards the end

npviewer.bin[2448]: segfault at 10 ip 00000000f62abc52 sp 00000000ffa7e310 error 4 in[f5e41000+b5f000]

See the phrase segfault this is a kernel crash and results in the cryptic last line in kdm log ddxSigGiveUp: Closing log meaning the X server doesn't start hence no screen picture. The file causing crash is npviewer.bin.

Can't really advise how to fix this.

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strange, would an error in libflashplayer produce a login loop? i mean this is the same for the other users as well and i can login with fresh created users without any problem. – Balázs Mária Németh Feb 19 '11 at 19:22
This has nothing to do with the problem, if you close a browser running Flash while Flash is doing something, npviewer.bin may crash. – Lekensteyn Feb 19 '11 at 20:47

It sounds like the problem is some setting/file in your ~/.kde folder, which is causing issues with KDE and nothing else. One solution would be to rename or delete that folder - this would reset all of your KDE settings to defaults and you could start from scratch. If you only want to clear out some settings, you can selectively rename or delete various sub-folders in your ~/.kde (most likely anything web browser related) until you find the culprit.

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