I came across an error using Data Compare tool, the same error happens in 2.0.009 and Beta 220.127.116.111.
How to reproduce: execute two times below SQL.
select * from sysobjects
Right Click in the either results grid and choose Compare to and select the other grid that contains exactly same output.
Under Comparison Key check all fields, run compare. Error: Unknown type found during storing data. Type System.UInt16