This is the final word on the 03 model of the modems.

They work fine with 7 series, they have a problem with DOS modem communication programs, Telix, old hyperterminal and RPRO 6 SERIES polling.

There is no fix for this. If they run across this problem they can only do one of the following

A: put in a different brand modem
B: put it a different speed modem ie 33.6
C: upgrade to 7 series.