You should not include your id as a hidden field. Autonumber fields should be left off the pages entirely when creating the insert and update pages.
The wizard will automatically add another hidden field to hold the ID and update the correct record. You are over-thinking it and it will actually cause issues. Just leave off the autonumber field and everything will work automatically. The wizard will automatically do what you are trying to add manually and by doing what you are doing it is more likely to cause issues.