Hello all on the thread! I just recently ran into a problem on my last video. FYI I have been editing on this software for 5 years and have never seen anything like this before. I rendered a video, then I watched it to review it before posting it up. when i realized that my overlay effects did not render with the video. I went back into Vegas to check the problem, to realize that everythingw as highlighted for render. I took a closer look at the effect tracks and found out they were magically muted. None of the other videos were solo 'Ed and the overlays were not muted on left bar I've tried practically everything and they will not unmute..
Is this happening with your other projects? If not, you may have a corrupt .veg file. You could always open the project with the mute issue and then open another new project, having two instances of Vegas running and copy and paste from the old one to the new one. Re-add the effects and match their parameters.