Please uninstall Urban Terror 4.0 and ioUrbanTerror 1.0 before installing 4.1. Back up your configs/demos/screenshots though. You can copy those back to 4.1 after it's installed, or you can start out fresh if you want. There's only FULL packages, no upgrades.
I would like to thank the following people for making it possible:
TwentySeven and BladeKiller, great work! Rest of dev team: dito! QA Team: pwn! File hosters: n1! 3rd party mappers: GG! People from ioq3 helping out: superb! Wolfseye's box art: zomg frikandel! And of course, the community: ROFLCOPTER!