Error opening file in Visio 2003

[Mark]

We are using Visio 2003 in our office. However, we are unable to open
certain visio files that were created in Visio 2002. When we try to open the
file(s) in Visio 2003, we get: "An error (1) occured during the action Open
File. Unexpected end of file."

We have even tried to using Visio 2002 to save the file as a different
version but still no luck with opening in Visio 2003. Has anyone seen this
kind of error and knows how to fix it? Any help is much appreciated.

Thanks.

Mark