Very small "Gaps" & clip fragments are what causes the timeline/transition/exporting problems with editing in all versions of PS. I have suggested flagging them with bright Red in the Render status line. That would solve 99% of all the problems in both PS21.5 and previous style editing, and PS22 style editing. The small gaps & clip fragments just go visibly unnoticed on the timeline and cause the majority of all problems.
It could be a configuration option to Red flag Gaps and short clips under a specified length in frames. This would also catch the small 3-4 frame clips that get pushed to the ends of adjacent clips during edits. These little 3-4 frame clips that flash during transitions.
Such a simple feature to add that would save countless hours of frustration exporting, and going back to fix transition issues, then exporting again, etc...