The greeter application appears to be crashing

A Fedora 7 installation recently showed this error when X was started:

"The greeter application appears to be crashing. Attempting to use a different one."

Googling for this one came up with few hits. The issue was quite simple, the root / mount had no space and was at 100% usage. I checked for the mount with the highest space usage and found that /tmp had the highest. A prompt rm -rf /tmp/* brought / back to 22% usage. Most probably this was due to the graphical yum updates. As soon as space was made available on / mount, the error disappeared.