Also, I found this at MacLedge:
"Ace posted what may be the solution to the problem for those who get no further than the interface. Look in your regular UT system folder, and if you find a file named "INF_iSoldier.int" delete it. I found it in the clean-install version I did, which wasn't working." And when starting up a bot match DO NOT change the Game Type to Infiltration 2.8, leave it the way it was, 2.8 will load automatically. Be sure to download the separate "Infiltration Mac Installer" from the Infiltration downloads page, and read the manual for installation instructions."
Don't know if it's exactly what you're looking for, but it sounds like good advice anyway.