Norine,
Can you clarify one thing?
Are the following still correct:
Opening Balance of the original Bank Statement
Closing Balance of the original Bank Statement
Line Item total and direction of the invalid Item (i.e., an incoming transaction for a particular amount)
If so, while you can't reverse a transaction on the statement, you should be able to reverse what the transaction was for. Even if it's a pre-selected item, you should be able to go into "Postprocessing" (even if it says "Not Required") and reverse the allocation. You can then post a new Payment Allocation for the appropriate transaction or amount.
I haven't run into an occasion where i haven't been able to correct a single line on a statement, so while this may be a special circumstance, i'd at least give it a try before you reverse 3 bank statements.