Hi Roxy,
As I only use "Single-Track Editing" and not the "A/B Editing" which uses three tracks of the Timelane namely Video A, Video B, and the transitions track, which is what you appear to be using, my answer may be of little use to you. As you probably already know in "Single-Track Editing" the transition is dragged and dropped into the joint between adjacent clips. This transition can then be "previewed" in real time by "Scrubbing". This is done by holding down the "Alt" key and dragging the "edit line" over the transition. The effect you see is not at full playback speed, and audio does not play, but you can see the effect the transition has, on the "head" and "tail" between the two adjacent clips in the timeline. Sorry but I don,t know if this works in "A/B Editing". This is similar to a problem I am having where the finished movie plays the sequence of clips and the transitions between them, but any "still images" dropped into the timeline, show up only as a black screen for the duration of the still image. Thus I get a movie sequence, then a transition, then a black screen where the still image should be, and then the next transition to the following movie sequence.
Perhaps someone reading this thread can tell me why still images will not render even though they play o.k. when viewed in the "Monitor" window. Can you have a transition inserted between a still image and a video sequence or is this what the problem is?