Stored Procedure Returns -1 For A Bit Field

Hello,

I have a stored procedure:

-- Get an individual league match by ID
ALTER PROCEDURE [dbo].[mb_League_GetLeagueMatchByID]
(
   @LeagueMatchID  int
)
AS
SET NOCOUNT ON

SELECT * FROM mb_LeagueMatch
WHERE mb_LeagueMatch.LeagueMatchID = @LeagueMatchID


The mb_LeagueMatch table has a column named IsActive that is a bit datatype.
The value for all rows is set to true (in database explorer in visual studio 2005).
When I execute the above stored procedure I always get -1 (I'm guessing that means null) as a result for IsActive if it was true and 0 when false (as expected).

However, when I run a query on the database for the same parameter, I get the expected 1 as the value for IsActive.

Has anyone seen this before?

Thanks,

Howard