virtualbox.org

Hi,
I installed VirtualBox with the relative programme Ubuntu.ova last Friday (2 October). Everything worked perfectly!
Then I upgraded my system to Mac OS El Capitan, and I opened VirtualBox. Suddenly it didn't work and it still doesn't work.
I tried also reinstalling both VirtualBox and Ubuntu.ova, but it didn't solve the problem.
Somebody can help me please?

thanks you all!

Start by reading the answers posted just a couple posts below yours: El Capitan?. Granted, your question had an exclamation point and the other thread a question mark, but you can still read what others have been saying about El Capitan compatibility and potential problems/solutions.