Cell of type integer won't clear - Exceptions, Errors, Bugs: "First, in Enterprise Manager, to set a numeric field to NULL, select the
field and then press ctrl-0 (zero). You won't see anything at first,
just move off the current row to see the NULL result. Deleting the
entry of a numeric field will always fail with the result you're seeing.
Also, try setting the field to null in query manager with a SQL query.
Those two things would let us know if the problem's in the database or
back in the code someplace."