LWW strange error

The users of a gui I built and re-delivered recently are now getting an error 
before the gui starts - something about can't load / find "CONCAT/OLE".

I can't duplicate this error on my machine.

They are running XP SP2, on machines where Lispworks is not installed.

I simply built a gui with CAPI, *without* explicit use of OLE / activex / 
whatever.  I'm using LWW 5.1.  I'm blissfully ignorant of the latest Windows 
terminology (e.g. I have no clue what a "manifest file" is and whether that 
might be a source for my problem - I'm relying on LW to shield me from such 
agony :-).

Does anybody recognize what might be causing this error and where I should 
look to understand how to fix it?

thanx
pt