Access database engine stopped the process because you and another user are attempting to change the same data

In this article, you will find that the error can be caused by the bit data type:

This problem occurs if fields with a bit data type in the SQL Server-based database have been left blank. Microsoft Access interprets blank fields as fields that contain Null values, and the Jet database engine does not release them. As a result, the records remain locked and are not available for deletion.

Note that you must always have a primary key or unique key to update data from SQL Server.

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I was getting this error even though I had no bit fields and no nullable fields. I stopped getting the error when I changed the DATETIME fields to SMALLDATETIME. The only thing I could think of was that Access mis-interprets the dates and then tricks itself into thinking that something else has updated the date. I thought this because I had seen another comment on a different thread that Access can round differently than SQL Server.