I just updated Kontakt last night and now it crashes on startup (it crashes my Host program as well....Nuendo)
I wrote NI about it and they said:
The problem is most likely an issue with your OS. The newest versions of our software require OS X.4 Since you are on 10.3.9 you are likely going to experience issues like you currently have. If you upgrade, these should disappear.
I really doubt this but I guess it is possible.
It does now state on the NI website that 10.4.x is required for Kontakt 2.2. Unless you really need any of the new features included with the update maybe you should just reinstall 2.1. I can tell you that I'm running Kontakt 2.2 on my G5 and my Macbook Pro with 10.4.8 with out any problems, and none of the other people I know off running Tiger have had any major problems, so it wouldn't surprise me if it was because of 10.3.