I have a second-generation 13" MacBook Air running Mac OS X 10.6.6 with a 2.13 GHz processor, 4 GB of RAM, and a 256 GB SSD hard disk. I often get failures when I attempt to copy a large file or large collection of files from an external USB drive (typically a "Firewire" generation Drobo) to the internal drive.

The failure behaves almost exactly as if I had pulled the USB cable from the computer in mid-transfer. I get a warning that I have removed the hard disk improperly. After this event, the drive no longer appears mounted in the finder, and I have to unplug and reinsert the USB cable to mount the drive again.

I have also seen a similar problem when using Aperture 3 to import a large number of photos and videos from a USB Compact Flash card reader. The import will fail and I will have to unplug the Card Reader and import the missing items.

Oddly, reversing the direction of the copy seems pretty reliable. I've never had a problem copying a large file to a USB device, meaning that I have quite a few large files which are stranded on my Drobo.

Model Identifier: MacBookAir3,2
Boot ROM Version: MBA31.0061.B01

I have seen a similar issue reported on Apple's website:

http://discussions.apple.com/thread.jspa?threadID=2648590&tstart=0

The only suggested resolutions there seems to be switching to another form of connectivity (e.g. firewire, which does not exist on MacBook Air), or downgrading to Mac OS 10.6.4, or reverting the USB kernel extensions to the 10.6.4 versions:

http://discussions.apple.com/message.jspa?messageID=12566073#12582956

I'm not too keen on the idea of downgrading kernel extensions.

Does anyone know of a hardware revision without this issue that I can trade up to? Are there any other potential solutions out there?