>What if:
>

>IF NOT EXISTS(SELECT column_name
>                     FROM INFORMATION_SCHEMA.COLUMNS
>              WHERE TABLE_NAME = N'Volunteers' and COLUMN_NAME = N'IsActive')
>   BEGIN
>        alter table Volunteers
>              add IsActive bit NOT NULL CONSTRAINT [DF_Volunteers_IsActive]  DEFAULT (1)
>   END
>

Didn't try that, though it doesn't address the original problem. I can drop the field and re-try this syntax, though.