Urgent-Issue with Payment Process

User tried to run a payment process and the build payments step errored with SQLERRM: ORA-06502: PL/SQL: numeric or value error: character string buffer too small.  We found the bank account that had been entered incorrectly and have corrected that on the supplier.  However, the system has all the payments in that run 'marked' as if they are paid so won't pull them into a new payment process.  We can no longer access that payment process (it has disappeared from the home page of the payment manager).  How can we terminate the process or get the payments to build?  Please