Has anyone noticed a black screen when finishing the quest crush the white legs i have tried everything i even got help from Bethesda but i haven't had any luck please help

This may sound nuts, but in Steam right click New Vegas and select propertys.
Go to the local files tab and hit the button "Verify Integrity of Game Cache".

It tends to fix some errors from bunged game files, ESM, BSA, and such.
For me doing it yesterday restored the voice of Doctor Mobius, Old World Blues, and stopped it from crashing when I spoke with him.

Hopefully you have a steam app device there to help.