OK, I'm a newbie but I think I know the answer to this one. You have to go and check which library references are available for the database. The only way I know to get there is to open up a module, hit F2 to open the Object Browser, then right click on the right hand pane and select 'References'. I know there's an easier way to get there, but that's the only way I can think of right now (this is in Access 97 by the way).
Anyway, compare the libraries that are selected in the two different databases. I'm willing to bet that there's a library in the first db that isn't selected in the second db.
Let me know if this was right,
Q-