Why do I get 80040E2F errors?

Microsoft OLE DB Provider for ODBC Drivers error '80040e2f'  [Microsoft][ODBC Microsoft Access Driver]Error in row

 
This can happen if you are attempting to delete records while looping through an ADODB.Recordset object. Use regular DELETE statements instead of ADODB.Recordset's DELETE method: 
 

<%      ' ...      conn.execute("DELETE table WHERE column ...")  %>

 
This will be more efficient code, and will alleviate the 'error in row' problem. 
 

Microsoft OLE DB Provider for ODBC Drivers error '80040e2f'  [Microsoft][ODBC SQL Server Driver][SQL Server]Violation of PRIMARY KEY  constraint 'PK_<tablename>'. Cannot insert duplicate key in  object '<tablename>'.    or    Microsoft OLE DB Provider for ODBC Drivers error '80040e2f'  [Microsoft][ODBC Microsoft Access Driver] The changes you requested to the  table were not successful because they would create duplicate values in the  index, primary key, or relationship. Change the data in the field or fields  that contain duplicate data, remove the index, or redefine the index to  permit duplicate entries and try again.

 
This is pretty straight forward; you're attempting to insert/update a row with a value that already exists, on a column (or set of columns) that is defined as a primary key. By definition, a primary key can only have one 'copy' of each unique value. Either investigate the coding logic that is generating these primary keys for insert/update, or re-examine whether this column should, in fact, be a primary key. If the column(s) should be a primary key, consider validating prior to insert... if someone is trying to insert a new row that already exists (at least in terms of the primary key), stop them BEFORE the error is tripped up. 
 

Microsoft OLE DB Provider for ODBC Drivers error '80040e2f'  [Microsoft][ODBC Microsoft Access Driver] You cannot add or change a record  because a related record is required in table '<tablename>'.

 
Sounds like you have a foreign key defined, and are not satisfying its requirements. E.g. if you have table Parent, with an Autonumber column, and table Child, with a foreign key that references table Parent's Autonumber column, you should check that you are inserting into table Parent first, and that any updates to table Child are still referencing a valid column in table Parent. (This should be done in the reverse order when deleting records... you should delete from table Child first, then the 'master' record from table Parent.)