AIB have said their debit cards are now operating normally at ATM machines, including non-AIB ATMs.
AIB customers with debit cards have been unable to use ATMs at other banks for the last two days, but yesterday the problem extended to AIB machines.
Cards which tried but could not withdraw the daily limit of €600 from other banks were then being rejected by AIB machines.
However, the daily limit was reset at midnight and a spokesperson for the bank says this problem has now been fixed.
AIB is continuing to monitor the situation very closely.
It is believed has been caused by a third party service provider.
AIB says anyone who is still having problems should get in touch with the bank's 24 hour banking number 01 269 50 22.