I recently installed Kubuntu in Ubuntu Desktop Environment. I've checked the diskspace left for System, it shows that I have 1.3 GB left. But after I restart and boot into Kubuntu, the system gave me the message something like this: My login session are not longer than 10 seconds, this might caused by some installation error or out of diskspace.

What should I do? I can't login into all the sessions and don't know what to do with the terminal (I don't know about linux commands...).