Complaints about overheating notebooks — Apple doesn’t call them laptops anymore for reasons that become obvious once you use them for a few minutes — surfaced soon after the release of both the MacBook Pro in early 2006 and the MacBook later that spring.

Now the problem is the new MacBook Air. Despite assurances from Apple (AAPL) reps at MacWorld that it ran cooler than its bulkier predecessors, Apple’s discussion boards are filled with messages about fans running a full throttle, machines overheating and occasional lock-ups. As of Thursday afternoon, the topic “MacBook Air Overheating” had been viewed 3,135 times and a second topic, “MacBook Air intermittent freezing problem,” had drawn 2,541 views.

“I spoke to Apple and the first thing I was advised to do was to remove all cables and the battery!” one user reported. Whoever was manning that help line apparently was not aware that the battery on the MacBook Air can’t be removed.

On Monday, Apple issued a software update — MacBook Air SMC Update 1.0 — that “fine tunes the speed and operation of the internal fan,” but reports of its effectiveness are mixed. One user said his machine had been relatively quiet since the upgrade. Another said it “didn’t work at all.” Others reported that when they tried to install it they were told that their MacBook Air was already up to date.

The broader problem, one suspects, is that Apple has once again put design considerations ahead of performance and pushed the new machine’s heat tolerance just a bit too far.