Inserting Nulls In To Table Conflicting With Rule

Hi,

I basically have two tables with the same structure. One is an archive
of the other (backup). I want to essentially insert the data in to the
other.

I use:

INSERT INTO table ( column, column .... )
SELECT * FROM table2

Now, table2 has a rule on various columns:

@CHARACTER IN ('Y','N')

but the column allows nulls, in the design view is says so anyway.

When I run this query I get:

A column insert or update conflicts with a rule imposed by a previous
CREATE RULE statement. The statement was terminated. The conflict
occurred in database 'database', table 'table', column 'column'.
The statement has been terminated.

Obviously, I've changed the names of everything.

The only data in those columns which could possibly conflict with the
rule is the NULL value. Any ideas why this doesn't work?

Thanks.