What is this:"dbx: internal error: modus 6 is not defined yet"?

[Christian S. Collberg]

We're running dbx under OS 4.0.3 and are experiencing some problems.
While loading symbols (?) dbx exists with the message:

   dbx: internal error: modus 6 is not defined yet

We're using the lightweight processes library and a home-rolled remote
procedure call library. The program is written partly in C, partly in SUN
Modula-2 (version 2.1).

Any ideas as to what causes the error or how to get around it would be
greatly appreciated.

Thanks,
Chris Collberg
collberg at dna.lth.se