Well as far as the memory area is concerned leave virtual at -1 and set physical to whatever you think is reasonable given the amount of ram you have. Set it in megabytes. Like 512 or 256 or whatever just don't put the entire amount of RAM you have.
The BPS and GRID settings have to do with the renderer. Just leave them alone. I do anyway.
Hope it works for you.
...and that is how I saved the world.