XIO: fatal IO error 4

[Robert Ken Francis]

Hello:

I get this error message when I exit out of the login window when I 
started using 'startx':

waiting for X server to shut down XIO:  fatal IO error 4 (Interrupted 
system call) on X server ":0:0"
    after 621 requests (619 known processed) with 3 events remaining.

How do I fix this?

Thanks
Rob