If you get a error like
Error: X session cannot start /tmp Error: unable to write to the /tmp
or similar errors to the above when trying to log into KDE
it could be because you have run out of inodes (the disk structure that allows you to create new files) or hard drive space.
I had this same problem, and after doing
to clean out of the temporary files that apt-get has used
and also since I am compiling up my own kernels, I deleted some of the
/usr/src linux-source linux-source-2.6.32
directories and then I was able to start up X, which is great.. something of a better error would have been better.. cannot create file, make sure that you have the space!!. sort of thing..
also sometimes if your X session does not start, if you delete your home directory (The user’s home directory that you are trying to login to) .Xauthority
because that is sometimes a lock on the xsession.