Suddenly my Vegas 17 didn't start. It hanged and I see the Vegas process in Task Manager.
I've uninstalled it and started new installation Vegas 17 pro build 455. It works without any problems till about 80%. And hangs when tried to register my serial number.
Have you installed anything at all recently on your system?..... If you did, uninstall and remove all traces of it/them. Also, when it hang, what exactly you saw on the screen, or, where did the start up progress line freezes?
Since Vegas 21 trial works, maybe that's an indication that its time for a needed Vegas upgrade.... By the way, do you have Borisfx Continuum Complete or Newblue Plugins installed for Vegas?