I took a brief video screenshot using Camstudio2 - avi.

I have just edited it in Vegas and rendered it, and find that it flickers on playback after rendering. When editing it, I didn't notice any flicker.

What could cause this?

I suppose there are many possibilities, but I'd immediately suspect a mismatched media / render property at some stage. For example, a conversion to interlaced, or a change of framerate.

As near as I've been able to determine, this sort of project works best when I start at the end and work back to the beginning. That is, determine the final display method, size, and framerate first, then apply that at every step along the way.

I recently did a software demo for a tradeshow display. Determining that the laptop to be used had a 1200x800 display, I decided on 8fps since I was adding some wipe transitions in Vegas. (Many software demos run as low as 4fps)

Therefore, the capture was done at 1200x800x8fps, these were also the project properties in Vegas (progressive), and these were also the render properties. This particular one went out in Windows Media 9 screen codec.

Screen captures are pretty unforgiving of size and framerate changes; this method is based on a single size and framerate from capture to delivery. Vegas is great for this work because it picks up most capture codecs directly without DI, and project properties can be anything you want.