I've never had that issue, but then again I don't usually play physical discs, just .iso files which become automatically unmounted upon a reboot, so I haven't experienced that issue. But I was having some sound issues since installing, and reverting back to the realtek 2.39 hdmi driver, so I reinstalled windows and everything else and now it works great. I was also previously having major playback issues with a couple of .mkv files that would only play smoothly on my machine with a core i7, but after installing media player classic - home cinema x64 edition and ffdshow 64 bit I can now playback those files with zero issues. I had previously found VLC to be among the best, but MPC-HC seemed to handle those files better, and you have many more options when it comes to using external filters for audio and video. Plus they are both freeware, and will play blu rays too, but I didn't try it on one of my media pc's so I can't comment on if or how well it can bitstream HD audio, but I'm pretty sure it can if it's setup right using the proper filters.