We have resolved this problem now for two clients. You definitely need SP9 or preferably SP10. Do you know if the Balance Utility has been run (at v4.3 migration or post migration for any reason?)? Do you find IZ Inventory Transaction records in ItemTransaction History? If so, what date is on those records? The IZ transactions are created to balance transaction detail history to ""current"" balance on hand. Depending on the date the utility is ran it can wack the Trial Balance and Item History Inquiry with a transaction that's out of sync with current operations.
At the end of the day, the existing IZ transactions may need to be deleted manually. Reopen closed years, change the Inventory System date to the way past, run the SP9 or SP10 Inventory Balance utility and allow new IZ transactions to post way back in time. Reclose and change dates back to current. Purge the transaction detail from the way back years which rolls up the IZ transactions. Then run Recalculate Item History to bring the Trial Balance and Item History Inquiry into sync with the current Valuation Report. (Whew!)
I usually knock out the IZ transactions in the live company first, then copy to a test company so the client can see the fix before executing in the live company.