Comment 47 for bug 269215

Not sure if this is the same bug or not but same error message.

/tmp became full.

Next time started up got the error.

Ran /usr/lib/libgconf2-4/gconf-sanity-check-2 from a terminal. Error message said could not delete file null and a subsequent line that there was a problem creating a file in /tmp.

sudo chmod a+rwx /tmp

On restart everything (well most things at any rate) were working again.

A few other things tried from the suggestions above without any apparent effect.