Lock condition... sort of

Where do I start... I am not 100% certain this is an RPG problem, but it
involves an RPG program, so here goes:

I have written an RPG application, using a display file and an RPG module
(pretty lengthy), and I will include this if necessary, but I first wanted
to see if anyone else has had this problem, and knows a solution, or a clue
they could hand off...

The user presses an Function key, and my display window pops up (a DSPF with
the ASSUME keyword in a format), they type in their data, press enter, or F3
to exit, and the main program takes over.  Perfect.

But sometimes, the user's screen "locks up".  When I say locks up, here is
what happens:  none of the F-keys work at the terminal, nor does the Enter
key.  They can type, but they can't press Enter or Sys Req, or anything.  No
input inhibit, nothing.  If they get a break message, they can F3 out of
that, but back to the "lock" condition. 

I have the Fkeys defined in my DSPF (at the file level), and I have
responses that work 99% of the time in my program.  

Tony Carolla
MedAmerica Billing Services, Inc.