I will just add a potential additional cause for those who had no luck with the video conversion settings or containers.
Check the sequence (tab at the top left of the window). I usually export when my window is showing the Video tab, which can be misleading.
I noticed that when I closed down my project, and then reopened it, the clip had been moved to a later time on the sequence. When I export, I get a whole bunch of empty (black screen) video, followed by a short time at the end of the sequence with my actual video clip.
I thought the whole thing was a black export, but then saw the sequence timeline and checked the very end of my exported video. Voila....there was the actual video. Only 20 seconds at the end of an almost 5 minute long video that was black for the first 4+ minutes.
Hope that solves a few peoples problems above. Probably us less experienced users who are running into the problem that can't be resolved with codecs or containers.
