I am using MS SQL Server 2000. I have some Nullable columns in my database table, and also I have bind a rule to those such that it can accept 'Y' or 'N'. So as per the SQL server behaviour these columns should allow 'Y', 'N' and also NULL. That is how it was working for the past few months. But suddenly these columns are not accepting NULL. If I try to insert NULL then its giving error saying "Creation Rule Violated". After two days it has started to work normally and allowing NULL. If anybody knows the reason for this abnormal behaviour of SQL Server please help me.

Thanks in Advance.