Yeah, doing a sudo rm -Rf /tmp/* should be safe. My system drive is 320 GB, but before I got in the routine of regularly clearing out /tmp/ I'd get such errors constantly once /tmp/ accumulated 2GB of temp files.
Worst I've noticed is that Firefox and/or Orca are a little more prone to crashing after I run my clean.sh script, and even then, I can't be sure its related to clearing /tmp/ and not something else in the script and even then, my tabs almost always restore properly, so usually, the most I lose is the minute or so it takes tty1 to drop down to the console following a crash and to relaunch my stripped down x-server.
