Macintosh boot speedup - rebuilding the kernel extension caches

This found on http://forums.macrumors.com/archive/index.php/t-1654766.html:

In Terminal.app:

1. sudo kextcache -system-prelinked-kernel
2. sudo kextcache -system-caches
3. Check that your startup disk is still correctly selected in settings
4. Restart your macintosh