Regarding the conversion error issue that I posted yesterday:

Tom, I tested the query on SQL 2008 R2 SP2 and SQL 2012 SP1, with the same results.

Paul, your explanation, along with...

Can anyone help me understand why the second and third selects in the following generate an error?

-- create a table with 3 UUIDs

DECLARE @tbl TABLE (id UNIQUEIDENTIFIER);

INSERT INTO @tbl VALUES...