Fax Sr. Client 5.2 viewer will not open

I have a co-worker who is having trouble opening a fax through fax sr. client. The error message says “Can’t run 16-bit windows program. This application is not supported by Microsoft Windows NT.” This is a very weird error because 1 week ago he hadno problems opening a fax. Nothing has been installed on the computer to cause a conflict. I’ve tried a total re-install and is still having the same problem. Why is it saying this is a 16-bit windows program?