The following is posted on HSBC's website:

"Please note that the following service will be unavailable due to required system updates. Please review the following date and time to minimise your disruption.

- ATM : Friday 13 March 2009, from 11:00pm to Saturday 14 March 2009, 11:00am

We apologise for any inconvenience this may cause."

There's a notice saying the same next to their ATM at Landmark. If I've understood correctly, the notice also goes on to say that ATM cards won't work in shops either during this time.

Words fail me.