To shorten the reviewing process, looking for something which will analyze the colors and making a simple chart of RGB over the video length, and frames which show an alteration will spike the chart
You could always use another filter to really boost the levels, then press shift-ctrl-[right arrow) in Virtualdub. In run through frames as fast as it can, and stop at what it thinks is a scene change (I think you can alter the threshold in preferences).
* though thinking about it, that wouldn't help if the change is brought in gradually.
DE