I follow the directions here carefully and all goes fine, but when I save or publish a custom form I get a page not found at the designated URL and the below error shows in the logs:

2012-09-27 12:27:56,077 [41] NHibernate.Util.ADOExceptionReporter - Violation of PRIMARY KEY constraint 'PK__orchard___3214EC0744FF419A'. Cannot insert duplicate key in object 'dbo.orchard_Common_CommonPartRecord'. The duplicate key value is (255).
The statement has been terminated.
2012-09-27 12:27:56,077 [41] Orchard.ContentManagement.DefaultContentManager - GenericADOException thrown from IContentHandler by Orchard.Indexing.Handlers.CreateIndexingTaskHandler
NHibernate.Exceptions.GenericADOException: could not insert: [Orchard.Core.Common.Models.CommonPartRecord#255][SQL: INSERT INTO orchard_Common_CommonPartRecord (OwnerId, CreatedUtc, PublishedUtc, ModifiedUtc, Container_id, Id) VALUES (?, ?, ?, ?, ?, ?)] ---> System.Data.SqlClient.SqlException: Violation of PRIMARY KEY constraint 'PK__orchard___3214EC0744FF419A'. Cannot insert duplicate key in object 'dbo.orchard_Common_CommonPartRecord'. The duplicate key value is (255).
The statement has been terminated.

When I look in the dbo.orchard_Common_CommonPartRecord table, there is no record with PK value of 255. The PK isn't an Identity column, but when I create a test page the PK value follows the failed form attempts indicated record id numbers, like they're actually there (ie: if I create a test page now, it will be numbered 256, though no 255 exists). Strange. Any ideas?

Thanks in advance for any help/tips!