Well, apparently it wasn’t a memory issue. I opened the file, copied the timeline contents and then pasted it into a new project timeline. I was able to render to both MPEG and WMV with no problem. The only thing I can think it was is that I had been using the same timeline over and over to produce several movies. I would delete everything from the timeline and add the new content, rename it and then render. Perhaps after doing this several times the file got corrupted or something?