That message usually means a reference is missing or broken, but if you're copying the db from one place to another, that doesn't make sense - unless maybe you're copying to a different pc. Then it would make sense as a possibility. Might help if you specified what you're doing when you raise that error.
IIRC, also possible to raise that error when event code becomes 'disconnected' from a control. That is usually fixed by clicking on the event in the property sheet for that control and if it takes you to that code it can re-establish the connection. A decompile then re-compile is sometimes another fix for disconnected code.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.