drum editor problem

Hi to all the members,

I have a problem with the cubase elements 9.I create an instrument track and choose kontakt 5 studio drummer vst.I open the editor to create my drums track and after a while while I composing drums in the editor the cubase exits on it’s own.Then I open again cubase elements 9 and my project has been lost and I have to start all over again.Does anyone knows why this happens.I have an iMac with 3,4 ghz,8gb ram and 1TB fusion drive and I can’t imagine that it’s my iMac’s problem.It’s brand new.Any suggestions,any same issues?I’m sorry for my english.