Apple has issued a statement confirming that some iMacs are suffering screen freezes since a recent software update was installed - but promises a software repair soon.

As reported yesterday, numerous discussion threads on Apple's support forums report that while the iMac display becomes unresponsive, the Mac itself appears to work normally, indicating the fault relates to the iMac's ATI Radeon HD card.

Confirming the fault - and promising a fix, Apple told Macworld this morning: "A small number of iMac users have made us aware that a recent software update issued by Apple can sometimes cause their iMacs to freeze, requiring them to restart their iMac."

The company explained: "We are tracking down the root cause of this bug, and will issue a software update which corrects it as soon as we can - most likely later this month. We apologise for the inconvenience."