I'm just going to throw this out here, there is actually quite a bit of discussion on this elsewhere. However, I was having both editing and rendering freezes when I had Vegas Dynamic RAM Preview Max set to 68% (I have 32 GB of RAM). I believe, by doing so I was actually stealing memory that Vegas needed to run efficiently, and certainly from other programs, I tried to run while waiting for the render to complete. My setting this value to 10% (I believe 5% is default) it seems to have fixed most of my issues.