My wife has a MacBook Air. One of the things that makes it so light is that it doesn't have an internal SuperDrive (writable DVD/CD). Apple sells a special external SuperDrive designed to specifically work with the MacBook Air.
Unfortunately, we couldn't get the SuperDrive to work. Any disc we inserted would be ejected, without being recognized by the computer. After a few days of struggling with this, we decided we'd take it back to the local Apple Store.
We live far away from civilization, and a trip to the Apple Store requires D-Day-like preparation. So, the SuperDrive sat on the desk for a while. Then my wife figured out the problem:
It was upside-down.
Yep, we were trying to use the SuperDrive when it was upside-down.
You see, Apple products aren't designed like other computer manufacturer's products. Most products have a shiny logo on the top of the product, and the bottom looks like a piece of Soviet military hardware. The MacBook Air SuperDrive has a shiny silver side, and a shiny side with an Apple logo.
It never occurred to us that the logo-side would be the bottom. She turned it logo-side-down, and now it works fine.
We feel really smart for figuring that one out. At least we didn't have to be told by a Genius at the Apple Store.