Pete: I found a problem. I can only get H.263 working and I have narrowed it down to QTConverter. QuickTime is set up according to your documentation.
If I run QTConverter stand alone, it looks like it works like it should, but it doesn't actually create the output file. Tried it with your QTConverter test example.
I think this might be why only H.263 works right now.
Thanks for your great work BTW!