Ok, I've done something stupid. : I've created a database with several related tables. The main database generates a serial number set to increment by one. I didn't make it unique (should have just didn't remember to do so), but didn't worry about it since the serial number is auto-generated and never seen by the users. What I'm finding when I do some work on the database, and then importing records into the modified version, is that the database creates duplicate serial numbers. Needless to say this is creating havoc in my relationships. What can I do to fix this?

You have to fix it manually, and reserialize the newer records. You can prevent this from happening on imports by using a combination of the Get(NextSerialValue) function and Set Next Serial Value script steps. (The exact spellings of these functions may not be right)