y'know I personally gave up on youtube on the NIT line years ago...even for the n900...every time you turn around sites like youtube , fb ...etc are constantly changing something... that makes it just that much more of a pain to keep up with... just to run their service.
For myself I transcode all my film via "media coder" and that gives me all my film desires in full screen happily. Batch conversion....easy-peasy . I even did a "foolproof-no-matter-what-always-works preset" for the n8x0 ...posted the preset here in the forums somewhere...just pop that preset file into media coder and it never forgets your preset ...even through version updates. Then you just choose the n8x0 preset ...drag and drop all your vids ...regardless of file type or parameters and presto-chango you got all your fav. film converted perfectly to the n8x0.
Streaming on the fly on the n8x0 ain't bad either for that matter...It depends on the site.

It's possible there is something current for the n8x0 that will work to allow youtube (that isn't outdated...)
It's possible the n8x0's hardware just can't handle the new youtube expectancies ...
I personally don't know ...
haven't looked in on n8x0 and youtube functioning in years...
someone else may know ...
or they have a good alternative ..
or an idea how to get 'er running smoothly for the n8x0's again...
See who chimes in with what.