Streaming DivX appears to be a very interesting technology (much better than FlashMovie I think), but saving directly to the posts table goes out of my imagination since it is completely wrong way. True I can't understand how it is possible to save a binary content in the plain text field.
I suppose much better way to show / attach videos to posts is to use
File Bank add-on, then to provide a link to the uploaded video and/or use special BB code to inserting it in the post via regular <object> tag or something similar.
But your method works for miniBB, it's also good :-)