I'm not sure which server behavior is giving you this error on your insert page because you have both a single insert and multi insert that are going into the same table with the same trigger. You should remove the single insert if you are planning on doing a multiple insert. Once you have done that you should run a test of inserting a single record to see if you get the error with only the multi insert.
On your update page it seems that your where clause is causing the multiple records to be updated. How have you configured this update server behavior? To see why it is doing this you can print out the update query. Attached is a copy of the page with the updated code to print out the query, load it and test it to see what you get.