Only thing that occurs to me is that you may be using backup software on the server that is not capable of "open-file" backup, and one or more people are staying logged in to the server and DBA overnight occasionally.

Thanks for the responses--they are steering me in the right direction.
 
I have received a new start_up.run file from DBA. I still have the problem
 
What I have found is that when I encounter this error,  start_up.run is hung up on the server, apparently preventing users trying to log on from doing so.
 
The user that has hung up the file is always a remote user. We use the GoToMyPc service to provide remote access to select users. Does anyone know of any issues or problems running DBA through GoToMyPc? Is there something that I can do to prevent or clear hung files?
 
Thanks.

DBA tech support said this was a corrupted network card - but that's not the problem (no access violations with any other programs). We reinstalled the ws setup on the machine having the same sporadic error message and that helped for a time, but the error is occurring again. There does not seem to be a common denominator and none of the posted suggestions are relavent.  
 
What else can be causing this on this one particular workstation????

Thanks for responding - I've sent your suggestion to our tech guy.....