SaveData Exception. Cannot insert the value NULL into column 'id', table 'dbo.items'; column does not allow nulls. INSERT fails. The statement has been terminated.

The error suggests that your database's "id" columns properties have been changed, and the id column is no longer an autonumber/identity and primary key column.  This would present a huge problem, since the id column was originally designed to have the database itself automatically assign a unique number for the record.  The error you are getting shows that the id column is not assigning itself a number, this can only be fixed by properly re-migrating a database from Access to SQL or by properly re-moving the database from one server to another using Microsoft's backup/restore procedures in The MS SQL management tools.  

If you have the original database before the move or conversion, Contact Us and have us migrate/convert it for you.