Cubase Crashing Please HELP!

Hi, I have cubase 7.5 and every time I load a big track, it keeps crashing and being really glitchy. I have a macbook pro 4gb intel core i5. If anybody knows how to fix this, please respond. Thanks!

What specific Mac OS version number are you running? Click on the Apple icon on the top left corner of your screen and select “About This Mac”.