The X window is not starting in FC6 and it comes up with an error that there is a lock file (/tmp/.X0-lock) that needs to be removed before startx will work. I can remove the file and startx then works but then I can not shut the computer down from X and the shutdown command does not work from the system prompt.
Why does the lock file exist if X is not running?
Any help greatly appreciated.

I believe the lock file is created once X starts, so that you can't start two X servers on top of each othre (hence the zero in the lock filename I think). That lock is there as long as X is running, and should be removed when X is shut down. This is how lockfiles are usually used. If you brutally force X to close so that it doesn't have an opportunity to remove the lockfile, the file is not removed. I'm not sure why it doesn't get deleted during reboot. Anyway, you should inspect what's wrong with the shutdown command; if you have X running, press CTRL+ALT+F1 (for example) to get into a console, log in (as root for a test) and issue shutdown from /sbin/, what does it do?

Maybe Xorg's logfile in /var/log/ has more information about what's wrong..

Thanks for your help, I found the answer. It is a bug and X starts but not on the screen that is visible. Pressing Alt+Ctrl+F7 gets me to the screen that has X running. I will get the updates that fix the bug and all should be sweet.