National Australia Bank says the technical failure that hung up millions of customer accounts for nearly a week has been resolved this morning, but transaction histories are still being updated.“NAB can confirm that all customer payments and transactions have been completed and all customer account balances are up-to-date,” the bank said in a statement on its online banking site. “Customers are able to transact as normal.”“Duplicated transaction histories are in the process of being updated,” the bank said. The problem which began Wednesday night, when a corrupted file halted the normal overnight data processing, stopping the pay of anyone who was due to receive funds Thursday morning, likely millions of customers.Attempts to restore the system also failed, leaving duplicated transactions and adding in unnecessary data on accounts, according to an industry source. The bank has denied human error caused the failure, which forced customers to go without payment from employers and Centrelink, triggering a wave of fees and penalties assessed for missed payments and overdrawn accounts.Experts however questioned the bank’s assertion that the technical failure was not caused by human error, suggesting the bank could be exposed to future troubles.University of Sydney IT professor Alan Fekete said yesterday typically databases should be able to function even if corrupt data has to be re-processed. “It’s possible to remain viable once a computer glitch kicks in by using a variety of hardware and by keeping records so you can untangle problems after the event,” he said. “In this case the system stopped operating when a file became corrupted, suggesting an oversight in the design of the wider IT systems.” One IT expert, who has helped implement and support systems at most of Australia’s major banks, said the banks claim that the problem did not result from human error were “rubbish.”“Computer systems do what they are told,” he said.  “If the attempt to restore the corrupt file failed, then that can only be because somebody had not tested the restore process correctly.”NAB said it plans to conduct a review of what happened.czappone@fairfax.com.au