http://www.sendspace.com/file/f24wsp
http://www.sendspace.com/file/1us6iv
So here are two files, one is the Leia shot encoded with UT Video YUV420 and the other with Lagarith YV12 - they both do the same thing as the WP in my MPC-HC; play with orange reds with default settings and correctly with optimal.
So I guess only RGB files don't play on optimal.
Also, I usually use the optimal setting, because many videos play with greyish blacks when I use the default settings.