I think I might be the friend in Chicago in this situation... or if it's a coincidence, I'm having a similar issue. We upgraded from WO 5.2.2 straight to 6.4.
The production computer (Windows 7), display computer (Windows 7), and projectors (two Sanyo HF15000's) are the same. The projectors are being fed directly from DVI/HDMI from the graphics card. Test content has included 30fps and 60fps, HAP and MJPEG I think. The video stutters, lags, refuses to play smoothly on WO6.4, though they played just fine under WO5.2.2
Additionally, when we push an update (Control-D), the production computer crashes. So that's fun.
Any thoughts appreciated, or any additional diagnostic tools I can throw at this thing to help figure out what's going on.
---Additional Info---
The full windows 7 tweaking guide was followed for the display computer.
I don't believe this to be a content-related issue because setting up 6.4 on my laptop (Windows 10), a different display computer (Windows 10), and hooking it to my HD monitor plays back all of the content just fine. In fact, in can play all of the test files at once, with some opacity tweening and chroma keying thrown in.