I come here tonight, hat in hand, ready to accept my humiliation and ridicule. They say the simplest solutions are the most often overlooked - I had upgraded my wad but failed to copy it to the korax directory (installed as a subdirectory of Hexen). Once that directory had the new wad, things worked fine.
As for editors, the only ones found in a cursory search of my archives (dusty boxes in the hall closet) were several on an old H!Zone CD. Tried the easiest one (simply called WadEditor) but, while it displayed maps and graphics nicely, couldn't find any reference to CLUS2MSG or lumps with it. A moot point now.