Since the launch of Apples latest laptop, the Macbook, there have been a number of rumours circulating of users who have been experiencing overheating problems and constantly running cooling fans. It appears that one of these users discovered that the cause of this was that a small strip of plastic covering a vent at the rear, designed to protect the internals from dust during manufacture, had not been removed before shipping.

As soon as he removed this the excessive heat issue was resolved.

Gizmodo have a report here