X server terminating

[Paul Kaplan]

Since installing Kubuntu 7.10, I've been having the following problem.

After a variable amount of inactivity (usually 15-45 minutes but occasionally 
well over an hour), the X server inexplicably terminates.  The only clue in 
the system log is:

kdm[5118]	X server for display :0 terminated unexpectedly


I've run Kubuntu since 6.06 on the same machine and never experienced the 
problem.

Any ideas what the problem might be or where to begin trouble shooting?

Paul