Are videos 83 onwards displayed in red writing in NED?
If so, perhaps they have not been downloaded fully. You can right click on a video name and select "re-download" to download only that individual video.
If this doesn't work I'd recommend you contact our lovely Support team directly:
With the following info:
What version of NED are you running?
What version of Quicktime are you running?
What version of OSX are you running?
They'll help you get up and running asap.