I am having the exact same issue, Acid 7.0 Pro works great, downloaded the trial of Vegas 13 and it’s unusable, audio skips a little if I do not move the mouse, as soon as I move the mouse, click or change the zoom level of the window, the audio starts skipping and stuttering. Completely unusable. I emailed Sony but since it was only a trial version, I don’t expect I’ll get a response. I also am running an M-Audio interface, and an NVidia video card. It seems to me like a conflict between the screen redrawing and the audio playback, but since it works fine in Acid Pro 7.0, it seems to be a software problem. I wish there was a way to run Vegas with the ASIO engine from Acid to see if that helps. I tried cranking my ASIO buffer up to 4096 and it only helps slightly, also tried increasing the buffer setting in Vegas, increasing and decreasing dynamic preview RAM in Vegas, etc. Nothing seems to make any difference except the ASIO buffer which only makes a marginal difference and still doesn’t make the software usable. Hopefully Sony addresses this soon or they’ll be losing current or future customers.