OTM Allowing Users to Approve Invoice more than once creating Duplicate Vouchers

We are on version 6.3.1 and are having an issue with duplicate vouchers. OTM is allowing users to approve invoices multiple times, creating duplicate vouchers being interfaced to the financial system. I am logging an SR with Oracle but am wondering has any ideas on a temporary fix that I could implement that would prevent this from occurring!
THANKS!!!
:eek: