So I sat here for a good 20 minutes trying to figure out why last week I could watch Chuck online and this week when I clicked on the episode to watch I would be presented with the NBC logo followed by a blank screen saying please pick an episode.
Anyways, I'll cut to the solution. If you have an altered HOSTS file and you're blocking the advertisement at the beginning the video will fail to load. I didn't look through all 10+ pages in the technical sticky post so I figured I'd just throw this out there for anyone else fustrated at being unable to watch videos.
The trick is to simply rename your hosts file for a short time and reload your browser. I suspect Firefox addons like Adblock and such block ads via the HOST file as well. Might try disabling that and see if you get any results. Hope this helps!