Strange behavior of HP-41CV with Math PAC and IR Printer Module

[Thomas Okken]

That sounds like an uber-bizarre conflict. Flag 21 has been the Printer Enable flag since day 1, so it sounds extremely unlikely that any program would use it for any conflicting purpose. Are you sure the problem isn't that the program is halting on a VIEW or AVIEW when flag 21 is set, while you're expecting it to keep running? I've run into that kind of problem with programs on the HP-42S as well.