Facebook video not playing?

Hello all,

I have recently made the jump to Android and picked up a new HTC One M8, moving from an iPhone 5. Loving the device overall, Android has certainly come along way since I had my G1...

The only issue I have come across is that video from Facebook doesn't seem to play. It might play a second of sound but then is frozen and the app becomes non-responsive. I have googled around this issue but havn't found anything so wasn't sure if anyone had any suggestions.

Also, perhaps a more general Android point, my first instinct was to uninstall and reinstall Facebook, but I don't seem to be able to - clicking uninstall on the Play store seems just to uninstall the update but leave the app. It was preinstalled as part of Sense 6 it seems (?) so can I remove it entirely to get a clean install?