Mac OS X v10.6.7 Supplemental Update for 13-inch MacBook Air (Late 2010)
Apple has released a rare Supplemental Update for Mac OS X 10.6.7, exclusively for the most recent edition of the 13-inch MacBook Air. The update addresses an issue that makes the system unresponsive when using iTunes, and Apple recommends it for all applicable MacBook Air users. The Supplemental Update is available via Software Update, or directly from Apple’s Web site. (Free update, 461 KB)
I don't think this problem is strictly endemic to the Air. Since installing 10.6.7, shutdown has been very slow on my iMac, and this morning, it wouldn't start at all until it'd been powered down and up.
Hoping Apple does something about this soon