I've found that turning on the Catalyst AI and setting it to advanced causes SL to crash immediately when I log in, at the point where it's finishing loading and it would show me the world if it were working correctly.
The Open Metaverse client will load, usually without crashing, under the same circumstances. However, I get a lot of pointy angles sticking out of my avatar at certain points and out of some other peoples' avatars at other points as well. My textures are also completely screwed up.
http://www.amaroq.org/Images/erronious.jpg
As compared to what I would have looked like.
http://www.amaroq.org/Images/AmaTux_001.png
The normal client I'm using is 1.23.122255, and the Open Metaverse client I'm using is the current 1.23 client. (Not the stable release one.)
In both cases, if I set the Catalyst AI to Standard, or turn it off completely, these problems go away.