I shot at widescreen (1920 x 1080), but need to crop to 4:3 aspect ratio for a web video. I've done this a bunch of times, but it seems I stumble up against issues occasionally -- such as this morning.

See if I understand correctly the sequence in which you do things really matters:
1st: set the dimensions of the project to a 4:3 aspect ratio.
2nd: crop the video event(s) to "match output aspect ratio."
3rd: when overlaying a title on a colored overlay at the bottom of the screen.... well, that's where I've been having recent issues. The overlay is hanging out over the edges of the video itself when I view the rendered output. But in preview, it looks fine.

Also: a related question: when I edit some event using pan and crop but do not want to use the timeline for the event, how do I avoid creating keyframes? Do I simply have to always start at the very first frame of the event?

Thanks for any suggestions.....
Orson