While editing the Programmonitor freezes

While editing the Programmonior freezes. It is just showing the one frame when it's happening. When press play, you can hear the sound of the edit but no movement in program monitor. After restarting Premiere Beta it helps for round about 10 Minutes. Sometimes the Program monitor is just showing a pink screen instead of the actual video, but this just happened 2 times, the freezing happens more often.