i've done this many times, using the same settings from the same basic template and fx.   tried different configs, output, buffers, rebooted... thought i saw something about this recently but nothing shows up on a forum search for mp3?... that also is odd.  
can i update the lame file?  
i finally got a render by disabling Fast Bounce, but it took several tries and kept getting the dreaded Audio Engine Dropout box.   I also deleted the Sonitus Gate plugs after I figured out they were not functioning at all.  
The next day... the file rendered fine using the normal All preset... go figure???

Have you tried disabling one plugin at a time until you find the one that could possibly be causing the issue? I know you said you use the same fx all the time, but maybe something has changed with one of them and is causing some problems. Just a thought. I hope you get it fixed.