For almost a month account holders with Ulster Bank have been unable to access thier online accounts or see details of deposits and withdrawals.
The problems started on June 19, the same time as parent bank RBS (LSE: RBS.L - news) suffered a computer failure . RBS resolved the issue within a few days, but the problem has taken much longer to fix at Ulster Bank.
For football coach Tim Wareing, who has a business account with Ulster Bank, the delay in sorting out the issue has been a shocking own goal.
"We've had cheques that have been paid out twice. They have since been corrected but in terms of my own salary, I haven't been paid since the end of June," said Tim.
The fiasco has forced Ulster Bank chief executive Jim Brown to turn down his annual bonus while branch opening hours have been extended to help customers.
No one from the bank was available to speak to Sky News but one of its managing directors, Stephen Cruise, has recorded a message on its website.
"Firstly, I want to say sorry for the disruption this technical issue has caused.
"I wanted to record this message to make sure our customers know how we can help, and reassure you that all our staff are working hard to put this right.
"Thank you for your patience and understanding. We’ve already helped 120,000 customers, extended the opening hours of many branches, trebled our call centre staff, and we’re updating our website regularly.
"We made a promise that no customer would be left permanently out of pocket and we intend to keep that promise."
Ulster bank has around 1.8 million customers in both Northern Ireland and the Republic of Ireland. It is thought at least a third of those have been affected by the computer glitch.
Ten branches across Northern Ireland were open for a few hours on Sunday to help customers. Twelve banks were open in the Republic of Ireland.
In an unprecedented move, branches also opened on Thursday, July 12 - a major public holiday in Northern Ireland.
Sunday and holiday opening shows just how extensive and damaging this crisis has been.
The bank has been criticised for not keeping to the deadlines it had set for fixing the problem. Its (Euronext: ALITS.NX - news) website now tells customers: "We expect that services should begin to return to normal from Monday July 16."
The week ahead will be a real test for the Ulster Bank. Customers and small business owners like Mr Wareing want to see it back on the ball, or it could find many of its supporters changing sides.