How can you think there's nothing wrong with Netflix and Hulu when they have the exact same problem and YouTube doesn't? Dailymotion is fine too. Same with Vimeo. Same with Winamp, Windows Media Player, and iTunes. The problem is the way Netflix and Hulu compress their audio from what I can tell.
The 3.5mm audio jack is stereo, and Windows 7 is configured for that. Everything behaves exactly the same way in Windows XP as well, which I'll be moving back to since 7 just kind of sucks compared to it.