Tell us about the part(s) of the video that flickers. Titles / text ? Any objects / text with very thin horizontal lines? Any severely contrasted colors next to each other (ie, red next to blue)?

Flickering often occurs because of interlacing. Most televisions divide the picture into two sets of alternating fields. Very quickly, the television displays one set of fields (called lower) and then it switches to the other set of fields (upper). This happens so quickly that your eye perceives it as one full image (or frame). Because of this, there are many things you have to watch out for when creating your video. For example, thin horizontal lines might be visible when one field is displayed but disappear when the other field is displayed. This is what we see as "flickering."

Computers (and some televisions, but nearly as many) display each image as a full frame. So, no flickering.

How to fix this depends on what's causing the problem. Sometimes it's a matter of using a different font for titles, or just using a larger size of text. Sometimes adding a very slight blur (only vertical blur is necessary) will do the trick. Also, both DVDA and Vegas have Reduce Flicker options. I've not used them before, so I'm not sure when's the best time to use them. But if you've got some rewriteable DVDs (or regular DVDs burning a whole in your pocket), try it out and see if that helps. In DVDA, it's on the Properties / General tab for every media, including menus.

Rob