Video Engine could not start playback error

I've gotten this error twice this evening:



'The Video Engine could not start playback because the clock is not locked. If this persists, try de-activating or removing Native plug-ins.' :(



I'm only hovering around 62% cpu but if the session sits for a few minutes that pops up when I press play, the cpu meter sticks at 100%. The only remedy I can find is to restart PT.



Using AVID DNxHD video through the desktop video window on a second monitor connected to main video card.



GPU option on in Prefs.



If anyone has any info it would be appreciated! Thanks