This question was answered a while ago by Nick Hope, but I am having a new, similar problem in Vegas 15 that doesn't respond to the solution- I have a huge editing project that was originally done in VEgas 13. When opened in 14 it had each cut one frame off. I used Nick Hope's solution of renaming the mxhevcplug folder and that fixed it in 14. But I have to use that original 13 file now in 15 and it is doing it again, and the same solution does not do anything. I have the last Quicktime installed on a Win 7 computer. A strange thing that happens is - if you look at the one frame off at the beginning of each shot, you cannot see the wrong frame on the timeline but you DO see it in the preview. The differences in brightness/contrast/plugins between the video tracks make it obvious. So it is a "phantom frame" or something. Can this be corrected? This is on latest version 15, fully updated win7 pro 64, last version Quicktime installed.