Hi,
you could include some kind of ReadMe file saying that MMULib.lha from aminet may be required as well.
Please look at my thread
http://eab.abime.net/showthread.php?t=91558. There is a possible explanation to what's going on in the very last post.
Some people may encounter same troubles as me (and 2 other user from that thread on REAL amiga) - so I think it is worth mentioning about that program.