I know for fact it won't render if there isn't enough room on the drive. If rendering images over 2000x2000 you need at least 100mb open. However if you have 36gb of HD space this shouldn't be the problem.....if texture maps are large say 2000 pixels or large in MB size it can or will slow down machines. Other than that....delete one thing try and render....if it does it still put it back and delete another. Try a scene without all of your basics and see if it does it..basically troubleshoot for the problem...see if it is a prop or texture or a poser function. Isolate it...then work around it or fix it.