When watching movies instantly on my pc, sometimes the video seems to stream slower than the sound. It gets progressively worse as the movie goes on, and it doesn't help if I skip around in the movie and have it buffer again. By the end of a 40 minutes tv show, the sound can get to be about 5 seconds behind the video.
I don't see this being a problem with my computer since I can stream videos from other sites without any problems, and some other videos on netflix work fine.
Edit: This is using Silverlight, and most recently it has happened on Numbers Season 5 Episodes 4 and 5