This is just an observation that I have made on my own computer so I don’t know if this is more widespread. Today, I was troubleshooting an issue when playing videos and the audio going in and out of sync (or maybe vice versa depending on how you anchor things). This was happening in Windows Media Player, VLC, QuickTime and iTunes.
Eventually, I narrowed this down to be a codec issue which I have since fixed however iTunes is still running in and out of sync. It was like the sync was a sine wave oscillating above and below the point of being in sync with the video going faster than the audio and the audio going faster than the video. At this stage I have not found a solution (although I have not attempted a reinstallation or repair of iTunes).
That said, I don’t normally play media through iTunes at all apart from when I want to play a video podcast on the TV and have iTunes sync the position in the podcast up to which I have watched.
I’ll keep working on it though and report back if I find a workable solution (short of a full format and reinstall).