I wouldn’t alter your actual movie just to get the DVD menu buttons right. I had this too; the black frame thing. So I simply used Vegas to render out the individual frames I wanted to use in the menu as jpg/bmp files (magnify timeline, select only the single frame then render region only) and used those in DVDA to replace the default first frame pictures in the buttons. Maybe there’s a better way within DVDA but I couldn’t find it.
Good luck!
Fred