l faced a problem with running the sony vegas 12 on windows 8.1 and the problem was that it was incompatibale so you just right click the vegas.exe and properties then compatibility then chose windows 7 it will run smoothy hope it helps
NB this is done after the program has installed without any errors or problems
Thank You! My SVP13 on a newer system with W-8.1 which had been running great for a couple months all of a sudden slowed to a crawl a few days ago. Switching to Win-7 compat mode did the trick.