Macbook Air crashes after El Capitan update
After installing El Capitan, my Macbook Air crashes :
Here I found the solution:
1. Restart Macbook Air and hold down shift (takes a while). The macbook starts in security mode. It will finish the El Capitan update.
2. Goto /System/Library/Extensions/ and find delete LivescribeSmartpen.kext.
3. Restart Macbook and problems is solved.