After looking through some articles, I found that deleting the mouse completely from your Bluetooth preferences and then re-discovering it has fixed the issue for me. At least so far. I've used it for 2-3 hours since and have yet to notice any lag. But in your situation, it's probably lagging a tad since the processor is being taxed by streaming/reading a dvd. But you should try deleting and rediscovering the mouse and see if that fixes the issue for you.
Like I said to the other guy, my guess is that streaming is taxing the processor causing your mouse to lag. I've noticed it a couple of times when streaming, but it wasn't nearly as severe as the lag I was experiencing yesterday. I'd rule a slight lag when streaming video normal, however severe lag might not be so normal. Try deleting the mouse and re-discovering it and see if that helps with video.
