Problem during after the crowbar collective loading sequence

I need help, After downloading public beta 1.0 for black mesa, in all of sudden afer the crowbar collective logo loading sequence, the screen turned into black, can someone help me please ?

Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valveā€™s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.