We have an Access database that was developed in Acc2003. It is broken up into the front-end and back-end. We want to upgrade to Acc2010, but found that in several tables the autonumber fields became corrupt(?). I then rebuilt the table structures in Acc-2010 and then ran a query to append all the fields, except the autonumber field, to the new table. When I added a record directly into the new table, all was ok, yet, when I opened the front-end and tried to add a new record I got a message "Addition of record with cause duplicate keys." After that if I tried to manually add the record in the back-end, then the new autonumber field had a value somewhere in the middle of the existing records. Once this happened, had to start all over again - rebuilding the tables. Has this happened to anyone else, if so, did you get it resolved?