Summary: I changed autoexec.cfg, but the old version still executed in addition to the new version. I reset to defaults using the option screen and now it works.
I created an autoexec.cfg file and put in some key bindings that I later removed. Then while playing the game I noticed a message that alias -laserjump couldn't be found. I double-checked my autoexec.cfg file which is really short and it was easy to see that I didn't leave any of the laser jump script. I tried the obvious things. I restarted the game, deleted the autoexec.cfg file, restarted again. No success.
I looked around on the forum and didn't find anything mention of this problem, but I did find references to other cfg files so I thought maybe Nexuiz was copying my autoexec scripts to another cfg. I couldn't find any other cfg files though. I checked all through the Nexuiz folders, my library preferences folder, application support folder, etc. Maybe the default configs aren't in a cfg on the Mac version?
I deleted the entire Nexuiz folder, downloaded and reinstalled. The same -laserjump message appeared. So there is some config file being stored somewhere that I can't find. Finally, I went to the options screen and reset everything back to the defaults and that worked.
Anyway, it would be nice to be able to alter my autoexec.cfg without worrying about an old copy being executed in addition to the new one.
I'm using Mac 10.4.10 on an Intel iMac and running Nexuiz 2.3. By the way, it runs great despite this little bug and I'm having a lot of fun. I thank the developers. Also thanks to the forum members for the nice support.