damn the torpedoes
 

Ok, it's 1o'clock here and I'm trying hard to make the 3ivx using BSPlayer or WMP 10. I have got 3ixv (of course), AC3Filer, and Matroska, installed. What's in God's name going on?

I don't understand what you want. Do you have a 3ivx encoded file and trying to play it, or you want to encode a file with 3ivx encoder using BSPlayer ?
Second is imposible.
First: if the file is encoded using 3ivx encoder then 3ivx decoder should decompress the movie. When you try to open the file, do you get any message (like can't open file or unknown format ) ?