Fedora Unmount Problem

[mylar]

I recently installed Fedora Core 1 on a Dell 4600 machine. Thus far the
install went fine and everthing is working great.

However I have one small problem. Every once in a while when I shut the
machine down the system will hang indefinately when unmounting the file
systems. This doesn't happen all the time, every so often it will just
hit the step where it says "Unmounting file systems" and it will just
stop dead. 

Any ideas as to why this happens ? I am using ext3 file systems.

mylar