Strange Datetime Conversion Error In Stored Procedure.

Hi Everyone,

I've been battling this for two days with no luck. I'm using SQL
Server 2000.

Here's the mystery: I've got a stored procedure that takes a single
varchar parameter to determine how the result set is sorted. Here it
is:

CREATE PROCEDURE spDemo @SortField varchar(30)

AS
SELECT dtmTimeStamp, strEmpName, strOld, strNew, strActionDesc
FROM ActivityLog
ORDER BY CASE @SortField
WHEN 'dtmTimeStamp' THEN dtmTimeStamp
WHEN 'strEmpName' THEN strEmpName
WHEN 'strOld' THEN strOld
WHEN 'strNew' THEN strNew
WHEN 'strActionDesc' THEN strActionDesc
END
GO

When I execute the stored procedure in the Query Analyzer, it works
perfectly ONLY IF the @SortField parameter is 'dtmTimeStamp' or
'strNew'. When passing in any of the other three possible values for
@SortField, I get the following error:

Server: Msg 241, Level 16, State 1, Procedure spDemo, Line 4
Syntax error converting datetime from character string.

Now instead of executing the stored procedure, if I copy and paste the
SELECT statement directly into the Query Analyzer (after removing the
CASE statement and manually trying each different value of @SortField),
it works fine for all five possible values of SortField.

Even though the error points to Line 4 of the stored procedure, it
seems to me that the CASE statement is causing problems for some, but
not all, values of the @SortField parameter.

Any ideas?

Thanks,
Jimmy