USB trackball multicasting with Vetra USB multicaster has been 100% reliable for me. I am using their PS2 models for XKey multicasting and keyboard switching and that too is 100% reliable.
I have also tried hooking up the XKey PS2 model to the PS2 to USB monoprice converter and then hooking that up to the vetra USB multicaster and that works reliably too. I imagine the problems with USB XKey broadcasting all relate to the programming over USB aspect.
Ziran