I was normaly playing in black mesa, but i close it for a while for updating Directx, so when i enter again to black mesa appears a white screen!
Help!
Reboot your PC, run the DirectX redist installation once again, then reboot your PC one more time and try runing BM.
In case the problem persist - report back with the screenshot illustrating the problem and specs of the hardware and software you have in your PC.