Both the DAO and the ADO object libraries define a Recordset object.  By
default, Access 2000-2002 sets a reference to ADO and not to DAO.  Even
if you later add a reference to DAO, it defaults to a lower priority
than the ADO reference, though you can move it up in the priority list.

Therefore, by default, a declaration such as "Dim rs As Recordset" is
going to be declaring an ADO recordset.  However, the Recordset and
RecordsetClone of a form in an MDB file are DAO recordsets, as is the
recordset object returned by CurrentDb.OpenRecordset or a QueryDef's
OpenRecordset method.  Hence, you get a type mismatch when you try to
assign any of these recordsets to the (ADO) recordset you've declared.
You may also get a compile-time error if your code uses one of the
properties or methods that belong to the DAO Recordset object but not to
the ADO Recordset.

To correct this, be sure you've added a reference to the Microsoft DAO
3.6 Object Library (via the Tools -> References... dialog in the VB
Editor), and either remove the ADO (Microsoft ActiveX Data Objects)
reference -- if you're not going to use it -- or qualify your
declaration of DAO objects with the "DAO." prefix, like this:

   Dim rs As DAO.Recordset

Incidentally, the Recordset object isn't the only object that is defined
in both the DAO and ADO libraries.  All of the following objects are
declared in both libraries, and should be disambiguated if you have
occasion to declare them:

 Connection
   Error
   Errors
   Field
   Fields
   Parameter
   Parameters
   Property
   Properties
   Recordset

Note: the following objects exist with the same names in the ADOX and
DAO models as well:

   Group
   Groups
   Index
   Indexes
   Property
   Properties
   User
   Users