SQL statements works in ISAPI in IIS 3.0 but not IIS 4.0 - please help !

I have written an ISAPI dll which queries a SQL Server database when it receives a POST request with the necessary parameters. However I get a DBException : Invalid column name "OCHOP" when the SQL statement is

SELECT * from table WHERE ib_stock_loc_no = "OCHOP"

Here the column name is supposed to be ib_stock_loc_no but it complains about an invalid column OCHOP !!

However this happens only on IIS 4.0 and not on IIS 3.0 !! I have SQL Server 6.5 on both the web servers running 4.0 and 3.0. And the ISAPI has been developed under Visual Studio 6.0.

Any help will be appreciated
Arun.