Apple has released a fix for the MacBook Air, which reportedly overheats because of problems with the internal fan.

Update 1.0 of the notebook's system management control "fine-tunes the speed and operation" of the fan, Apple said in releasing the software Monday. The underperforming fan apparently caused the MacBook Air, which was released in January, to overheat and then lockup, leaving the machine unresponsive for 10 to 15 seconds or more.

Over the last two weeks on Apple discussion forums, Air owners reported problems with their computers freezing up.

One owner reported that his Air would lock up while he was watching videos, a CPU-intensive task that would cause the microprocessor to generate a lot of heat. The user said the system's CPU monitor showed that one core would shut down, shifting all the work to the remaining core. As a result, the system would stutter or freeze.

"This looks very much like a heat issue," another Air owner wrote. "Unpredictable behavior in a notebook is commonly caused when the machine is running too hot."

Besides freezing during video playback, some Air users reported the same problem while running Firefox or Safari Web browsers. "It's so annoying," one user said. "It's like first the computer is running fine, and then it slows to a crawl."

In building the ultra-slim, ultra-light MacBook Air, Apple stretched engineering boundaries to the limit. In January, the company warned buyers not to attempt to use software from older Macs to install the new laptop's operating system. "The Mac OS X 10.5 installation media that shipped with your MacBook Air is designed for use on this computer only," Apple said in a support document.

The MacBook Air lacks an optical drive, so users who need to reinstall Leopard must do so via Apple's external SuperDrive. Like the installer, SuperDrive works only with the MacBook Air.