Installation of upgrade El Capitan v10.11.3. going wrong

I have tried to install twice this update: El Capitan v10.11.3. I always got same result: a white screen with the cursor showing and nothing else. I thought I had interrupted the installation the first time so weeks later I tried again and allow it to run for hours. No luck.

I had to go back using my time machine back up. Any thoughts?

Thanks,

Mili