Why do I get 80040E54 errors?

Provider error '80040E54'  Number of rows with pending changes exceeded the limit.

 
This error can happen if you affect too many rows with an objRS.UpdateBatch call, or an ADODB.Recordset opened with adLockBatchOptimistic. Please, do yourself a favor. If you want to update rows in a table, use this methodology, instead of an efficient loop: 
 

conn.execute("UPDATE table SET column='value' WHERE [...]")

 
Using a recordset, which is meant for *retrieving* data, to enforce updates on a table is wasteful, and leads to errors such as this. For more information on avoiding a recordset for non-data-retrieving operations, see Article #2191. 
 
If you absolutely must use an ADODB.Recordset for updating rows, I encourage you to read Article #2191 again. If you *still* find that you need to do this (e.g. pointy-haired boss syndrome), make sure you break it into chunks, use a static or keyset cursor, and be sure that you always close your recordset objects / set them to nothing.