Ever since i replaced the factory 120-GB HDD in my Rev B MacBook Air with the 128-GB RunCore, the MacBook Air has been suffering from occasional hang. The hanging symptoms are: spinning beach ball in Safari, follow by spinning beach ball in all other apps, and eventually, the mouse pointer would not move. The only recourse is to press and hold the power button to turn it off and then press it again to turn it on. Unfortunately, there isn't any error messages.

Has anyone else seen this before?