There seems to be some problem with pIRender in the AVI area. I just checked it myself (I don't use pIRender very often), and I get an error message about the "H263 codec maximum size is ___ x____, please choose another codec", but the AVI options still displays after that. Then, I notice that at least one of my codecs is not listed there.
I thought that maybe the project that was loaded had a weird stage size which wasn't compatible with some codecs, so I unchecked "autoload" and restarted pIRender so it loads with no settings, but it gave the same results.
The only thing I can suggest is to render an image sequence with pIRender, then use another app to make it into a movie (if needed).