I've been having this problem the past week and I can't seem to figure out why exactly it's happening. The good news is that it doesn't crash! I will get a slight halt when the RAM Preview says it is mixing the audio and then the close/re-open behaviour. The reason I describe it like this is that the application window disappears and then the icon reappears to the front of the taskbar as if it had been re-opened again.
Since it's not crashing it's not a major issue however is does become quite annoying when having to quickly review a lot of little changes one after the other. Does anyone have any ideas?
YOu have not provided any system info or other technical details, so we can't really know. A common guess would be driver issues with your audio and graphics hardware...