Allied Irish Bank (AIB) has apologised after some customers in the Republic were unable to withdraw money from ATMs.
They had problems at the bank's cash machines because they were mistakenly registered as being over their daily limit.
A statement from the bank said: "We are investigating this issue and are taking all necessary steps to resolve it as quickly as possible.
"AIB apologises to all customers for any inconvenience caused by this issue."
The bank's customers using AIB ATMs could be affected if they have previously attempted to withdraw funds at a non-AIB ATM earlier in the day, where the total value of their attempts was greater than the daily 600 euro limit.
An AIB spokeswoman said: "The issue still remains with non-AIB ATMs. People are only affected at AIB ATMs if they had previously tried to withdraw cash."
She added: "Customers are able to use their AIB debit cards to withdraw cash at AIB ATMs, point of sale terminals and online shopping channels."
A spokeswoman for AIB said: "We can confirm that AIB debit cards are now operating normally at ATM machines, including non-AIB ATMs. AIB is continuing to monitor the situation very closely."