plpgsql won't work

Hi,

Using PGAdminII I created the plpgsql_call_handler function pointing it to 
the plpgsql.dll file.

Then I created the language pointing it to the handler, clicked off trusted.

I then created a very simple procedure:

-- Function: sales_tax(float4)
CREATE FUNCTION "sales_tax"("float4") RETURNS "float4" AS ' DECLARE 
subtotal ALIAS FOR $1; BEGIN return subtotal * 0.06; END; ' LANGUAGE 'plpgsql';

Then I called it using an sql window:

select sales_tax(45);

When I execute the statement the main window says executing query, a few 
seconds go by and then it says executing query...Done.  and I get
this error:

An error has occured in pgAdmin II:frmSQLInput.cmdExecute_Click:
Number : -2147467259
Description: Error while executing query;
No response from backend;
Error while reading from the socket

Any ideas? I execute a plain 'sql' function and it runs fine. plpgsql won't 
run.

Any help would be appreciated, I don't know if it is a windows problem so I 
posted here first.

Thanks,

Warren