It's a part of the copy protection (or whatever) of OS3.9 (and 3.5?). I think it's supposed to disable anyone from running stuff from OS3.9 on <3.9 WB. Can't remember what trigs it though. It will also kick in when booting without startup-sequence and doing a C:LoadWB. Or whatever; I know I managed to trig it a few times when experimenting with the startup..
