My MacBook Pro Retina is freezing a lot after upgrading to el capitan. I have clean installed the OS and it is still freezing. The pointer becomes unresponsive i can move it but cannot click anything and usually after a few seconds the entire system freezes for about 45 seconds.I have downgraded back to 10.10.5 Yosemite and the freezing is non existent. Is anyone having similar problems? My macbook is a 2.5Ghz 15 inch mid 2014 with nvidia.