The Barclays online banking website has been offline since about 8am BST this morning for reasons unknown.
A spokesperson for the bank said that the issue was "still being investigated", and they didn't know yet what had caused the site to fall over, but none of their other computer systems are affected.
The site is telling customers:
We're currently experiencing technical problems in Online Banking that mean some of you may not be able to log in to the service. We apologise for any inconvenience this may cause and suggest you try logging in again later.
And the spokesperson said the site would be updated with messages on how the fix was progressing.
"They're working hard to restore the site," the bank's spinner said, adding that customers could still get their balance from cash machines, over the phone, or (in a cheeky little plug) the newly launched Pingit app. ®