What operating system are you running? I think firstly, I'd try adding some more memory. 2000-XP can handle 2GB and Vista double that, so personally, that'd be my first fix. I was already at 2GB on XP Pro, so I had to find something else.
For me, a couple things worked. I was lucky in that I labeled all my assets in a way that I could it wasn't too much of a problem to do a brand new project, and just complete the thing in one session. If a brand new build is out of the picture, I also had some success by transcoding some of my larger video assets before building the DVD.