OpenSCAD difference sometimes shows huge green objects, sometimes not

I've read that when you do an F5 compile, difference() will show green objects that are being removed. For some reason openscad only does this sometimes. Most of the time, when I hit F5 everything is removed like it should and I am left with only the modified object left, which is great. Unfortuneatly as my design increases in complexity I now only get giant green objects when I hit F5 and am forced to wait a few minutes every time I make a change so that an F6 compile and render can complete. Any ideas what's going on?

Thanks

edit: apparently it was an issue with the preview mode of openscad. I fixed it by adding this before the seciton that created the problem part:

render(convexity = 2)

Edited 1 time(s). Last edit at 04/20/2011 02:54PM by inh.