As per unanswered StackOverflow and EF Forum questions:
http://stackoverflow.com/questions/12946512/
http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/a1059c15-bfaf-42e9-9bee-509273278300/
In short, using .NET 4 and EF 5, without .NET 4.5 installed, updating a child entity results in an unexpected update of only the [Timestamp] property of the parent entity (when the parent entity was in the DbContext).
http://stackoverflow.com/questions/12946512/
http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/a1059c15-bfaf-42e9-9bee-509273278300/
In short, using .NET 4 and EF 5, without .NET 4.5 installed, updating a child entity results in an unexpected update of only the [Timestamp] property of the parent entity (when the parent entity was in the DbContext).