in early October that some iMac users were experiencing freezing problems with their machines. The root cause of the freezes was traced back to the drivers used for the ATI Radeon HD graphics cards included with the iMacs.
"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," said an Apple spokesman in October.
Apple didn't reach their October estimate for releasing the update, but it's doubtful that many will complain that the update is available a few days into the month of November. The update is listed as "recommended" and is for 20" and 24" iMacs with 2GHz, 2.4GHz and 2.8GHz processors.
Apple has two separate updates available for download:

Download:
iMac Software Update 1.2 (Tiger)
Download:
iMac Software Update 1.3 (Leopard)
News source:
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