My first suggestion would be to minimize the variables which might be contributing to the error message.
Can the Foxpro program write to ANY printer on the COM1 port?
Have you tried putting another "generic" serial printer on the port and printing to it. If you are successful, then, regardless of what the error message is telling you, the problem is not Foxpro writing to the COM port. Instead it would most likely be a communication problem to the Intermec printer.
It has been a long, long time since I did any work with the Intermec printers, but at that time Intermec had its own very unique programming/communication language needed for bar code printing. If that unique communication language situation still exists, you might need to look into what serial data string your application is sending to the printer. Since you are working with a DOS environment application you cannot depend on a Windows driver providing that information for you.
You have also not told us if this application used to work and has now quit working - or what. Perhaps some additional investigation on your part and some more information for us might help us find the source of the problem.
Good Luck,
jrbbldr
jrbbldr@yahoo.com