One of the clips on my timeline are marked "media offline". Strangely, when I play through the clips in the edit room it's there despite of that the thumb says that it's offline. I can play the clip in the color room too, but sometimes (not always) the screen flash media offline. Any idea what is going on? It's not a timecode / clip conflict as I don't have any options or opportunity to right click and change the source clip.