Default constraint not working

[Seth Schrock]

I have three bit fields in a table that I have set to NOT NULL so that I can link to the table from MS Access. On each of these three fields, I have setup default constraints to set the value to False (0). This has been working for over a year now. All of a sudden, they have stopped working and every time I try to add a record to this table through MS Access, I get an error message that says Cannot insert the value NULL into column 'AppraisalRequested', table 'LoanTracking.dbo.tblAppraisals'; column does not allow nulls. INSERT fails (#515) I have tried removing and re-adding the constraint to the field and that doesn't change anything. Here is the script I used to add the constraint:

ALTER TABLE [dbo].[tblAppraisals] ADD  CONSTRAINT [DF_tblAppraisals_AppraisalRequested]  DEFAULT ((0)) FOR [AppraisalRequested]
GO

I'm using SQL Server 2005 currently.

[onlinetuition]

Did you upgrade database server/driver or installed multiple versions ?

[Seth Schrock]

No, there was changes made. No restore from backup, no server updates, etc.