Open Question: My Sony Vegas Pro 9 keeps freezing up while I'm editing my video! What can i do to stop this?

Yeah, It works fine and all, but I'll be sitting there editing my video, when all the sudden it freezes. I'm wondering if this is my processor, but this is the first time in a few years of owning this program that this has ever happened. I constantly have to save my project every little bit of progress i make, so that when it freezes, i can alt+ctr+Del And end the process, open it back up, and continue with my project. If anyone can tell me why this is happening, or possible problems that can cause this, id be happy to know. Thanks -Nick