After upgrading to El Capitan (10.11.2) my 2010 Mac Pro (Radeon 5770 card) has trouble waking from sleep. The machine wakes but there is no video signal (I'm using 2 monitors with the mini DVI ports). It is somewhat inconsistent, but the longer the machine is asleep the more likely it is to have a problem. The keyboard and mouse seem responsive. Any others experiencing this and have found a workaround?