XOpenDisplay sporadically hangs with no errors

[Dan Rather]

No computer h/w s/w changes for the last year.  Suddenly, xwindows program
that have run for years get to the XOpenDisplay function, and the process
hangs.  Getting PID from ps and using kill command doesnt kill it.  I can
go to windows task manager to kill it.  Some past compiled xwindows
programs work all the time, but not when I recompile them.  Newly compiled
programs has started successfully a few times, not often though.    I have
tried everything, and can think of no further ideas to troubleshoot reason
why it happening.

Any suggestions?

Thanks for any input.
Kyle