Upgraded transactions cannot be accounted

I have a client who recently upgraded from 11.5.10.2 to R12.1.1.  Right before the upgrade they voided some old payments and subsequently cancelled the invoices, without informing us and without generating the accounting.  Since the upgrade, we're not able to create accounting for these voided payments.  We've had to sweep them into the next period for 3 months now just to be able to close the AP periods.  I've been working an SR with Oracle for 9 weeks, and we can't seem to resolve the issue.  It appears that we have some missing links in the XLA tables, but determining what those