Some Ulster Bank customers are claiming that money has disappeared from their accounts.
One woman said her account is now "in a minus" even though she was paid yesterday.
The bank has confirmed some money lodged after Friday isn't showing up in accounts and some customers are incorrectly overdrawn.
Ulster Bank has stressed the most recent problem was not an IT failure and had no connection to the 2012 system issue.
Others are reporting that their cards have been declined, while lodgments aren't showing up.
It came as the boss of TSB - owned by Spain's Banco Sabadell - apologised for an IT fiasco that has seen customers locked out of their accounts and unable to make payments for four days.
Social media has been flooded with complaints today (24 April) as Ulster Bank customers noticed that payments - including salaries - had disappeared from their accounts.
Manchester United advance to FA Cup final
How much longer will he resist advances from clubs who offer a greater prospect of glory? "It just takes time". Tottenham is a completely different club to others and in the past four years we have been in a process.
A different spokesperson said that "no customer will be left out of pocket and should any external expenses be incurred these can be looked at on an individual basis".
Ulster Bank say emergency cash is available to customers and they're trying to fix the issue.
'We are investigating this issue as a matter of urgency and apologise for any inconvenience caused, ' it added.
When asked what kind of fine could be imposed in this instance, Minister Donohoe said it was a matter for the Central Bank.
When asked about branches staying open later for customers this evening so they can access cash, the bank said they would close at normal times. "If you would like to contact us please call 1850 424 365, get in touch via webchat or alternatively visit your local branch".
"Ulster Bank now needs to put its customers first".
At the end of March Ulster Bank also reported delays in payments being processed.