Bingo...works perfect. Justin, it looks like your the brains behind this whole deal, and man I am really impressed! At every turn there is a new feature or something cool that is unexpected that just blows me away. I simply cannot say enough......
Okay here is what I was able to figure out. My scenairo was this. I mixed and edited a project on another machine. I then consolidated the entire project and put it on a flash drive. I copied the entire folder onto a my home computer, did some additional edits and saved the project. I rendered to wav and everything went fine. When I rendered to mp3, Reaper crashes. I just now tried it again but changed the location of the output file and it worked just fine. I realize it is a set of kinda weird circumstances but at least now I know what to do. I also tested mp3 with both new existing projects on this machine at it all works fine. Best I can guess is it has something to do with the directory that is created on consolidate. Not a serious issue, but testing the weird cases is good, right??