Reply to Problems with MIDI Fighter + VCI100se combo?

So I'm trying to use the VCI100SE and the MIDIFighter on the same USB hub on my Mac Pro running OS X 10.5.8 and Traktor Scratch Pro 1.2.4 but I am having disturbing problems like the system is overloaded. After about five minutes of playing the sound completely drops out and the screen freezes for a few seconds, and then it keeps coming back and freezing again until I quit the program or unplug the MIDI controllers. Am I trying to do too much with a USB hub? It doesn't seem to matter if the hub is plugged in or not. Is it possible there is a problem routing MIDI out to both devices? I am using the official tsi files from this site for both products. Is anyone else having problems using these two together? I'm playing out toevening and sadly going to have to leave the MIDI Fighter at home....