<p>Does SQL Server CheckSum calculate a CRC? If not how can I get SQL Server to calculate a CRC on an arbitrary varchar column?</p>

I don't think T-SQL gives you the option to specify using a proper CRC as your checksum function. FYI, SQL Server Integration Services (SSIS) does have a "Checksum" transformation that gives you a choice of what checksum algorithm to use, and one of the choices is:
CRC32 - Using a standard 32-bit cyclic
  redundancy check (CRC), this provides
  a more open implementation.
To implement a CRC in SQL, you can either write a pure T-SQL implementation of CRC (fun!), or (if you're using SQL Server 2005 or higher) write / find it in another .NET language and then use that class as a compiled SQL stored procedure.