HSBC banking services appear to be offline worldwide, with users on Twitter reporting problems at ATM machines, making card payments in shops and with phone and online banking too.
Update: HSBC has tweeted that its card terminals and Internet banking should now be back on.
We called HSBC, who told us it was, "aware that some customers have experienced difficulties and we're looking into it across all our systems."
We're sure more will emerge on this story soon. HSBC boasts that it has around 100 million customers worldwide, many of whom will find themselves struggling to get money out today or transfer cash online. Many will be finding their cards declined in shops.
The HSBC UK Press Office has tweeted, "We are experiencing some problems - sorry for the inconvenience. Please follow for updates".
The biggest question on customers' minds will be when the system will be fixed. The outage is reminiscent of the BlackBerry Messenger downtime last month, which saw BlackBerry owners without the service for the best part of a week. If HSBC doesn't get online soon, those who use the bank could find themselves stranded without transport, or with no way of buying food.
Angry users are taking to Twitter to express their displeasure at not being able to access their cash, and at the bank's lack of information on what's gone wrong. One says, "Come on #HSBC you can do better than that. At least let people know. It's Friday and it is the time when we need cash more than anything."
One Twitter user simply writes, "I NEED TO EAT #HSBC".
Another tweeted "Now want to go back and tell the smart alec Tesco cashier than I'm not in debt or using a stolen card, it's HSBC who's systems have crashed."
Are you an HSBC customer? Let us know if you're experiencing trouble -- and what you think HSBC should do to fix it -- in the comments below, or on our Facebook wall.