converting .rmvb--update mplayer?

[user543]

I have a bunch of .rmvb files I'd like to convert to divx (or xvid) via mencoder using ffmpegx. I installed the latest ffmpegx and the RealVideo codecs as instructed, and all but one of the files converts properly. The last quits about 2/3 of the way through. Here's my question, without getting into the details of the log messages and errors and stuff. When I press "Play" on the ffmpegx summary page, this particular file fires up mplayer, but then mplayer quits abruptly, and the video doesn't play. Is this a setup for a failed conversion? I have other real files that also do this, but converted just fine. Now, when I download the latest independent standalone version of the mplayer application (1.0rc1) and install the real codecs, the video actually plays just fine. Does this mean anything? Is it possible that the 1.0rc1 is a more updated version than the one in the ffmpegx binary package and would work better for the conversion process? And if so, is there anyway to update the mplayer binary that ffmpegx uses? (In my simplicity, I tried to copy the file in the Package Contents of the mplayer 1.0rc1 application package into the ffmpegx Application Support folder and rename it to "mplayer", but this didn't work at all).

thanks,

[user543]

BTW, I'm assuming that mplayer actually has a role in the conversion process. I could be completely wrong.