а запросы одинаковые в обоих формах?

Recordset is not updatable - такое часто бывает, когда:
а) нет первичного ключа
б) в запросе есть группировки (хотя бы join'ы к запросам с группировками)
в) не помню, но еще есть случАи...

Вот, из хелпа аксессовского кусок:

Determining When Query Results Can Be Updated
In many cases, you can update the result set. However, in some cases you cannot.

In general, in order to update results, the Query Designer must have sufficient information to uniquely identify the row in the table. An example is if the query includes a primary key in the output list. In addition, you must have sufficient permission to update the database.

If your query is based on a view, you might be able to update the data. The same guidelines apply, except that they apply to the underlying tables in the view, not just to the view itself.

Note The Query Designer cannot determine in advance whether you can update a result set based on a view. Therefore, it displays all views, even though you might not be able to update them.

The following table summarizes specific instances in which you might and might not be able to update data in the result set.

Query Can be updated?
Query based on one table with primary key in the output list Yes (except as listed below)
Query based on a table with no unique index and without a primary key Depends on query.
Query based on multiple tables which are not joined No
Query based on data marked as read-only in the database No
Query based on a view that involves one table with no constraints Yes (except as listed below)
Query based on tables joined with a one-to-one relationship Yes (except as listed below)
Query based on tables joined with a one-to-many relationship Usually
Query based on three or more tables in which there is a many-to-many relationship No
Query based on table for which update permission isn't granted Can delete but not update
Query based on table for which delete permission isn't granted Can update but not delete
Aggregate query No
Query based on a subquery that contains totals or aggregate functions No
Query that includes the DISTINCT keyword to exclude duplicate rows No


In addition, you might not be able to update specific columns in the query results. The following list summarizes specific types of columns that you cannot update in the result set.

Columns based on expressions


Rows or columns deleted by another user


Rows or columns locked by another user (locked rows can usually be updated as soon as they are unlocked)


Timestamp or Image (OLE Object) columns