Best Practice for Correcting Translated Amounts

I was hoping someone could provide a best practice for making corrections to amounts that were translated in a prior period. For example: We recorded an accrual in AUD to the wrong account in Jan-11 and translated  the trial balance to USD in that period. Later in Jun-11 it was discovered that this error was made to the wrong legal entity so it was reclassified to the correct entity. However,  the translation rate between AUD and USD changed significantly since Jan-11 thus leaving behind a large FX gain/loss in the first company.

Question: Is there a best practice for eliminating the fx gain/loss in the first entity since none of the gain or loss should have been reported there, and move it to the second company? It should be assumed that we cannot reopen every period back to Jan-11 and retranslate all months.