Firefox Mac vs. Windows

I’ve got some serious JavaScript_age_ going on with my site: I sometimes wonder if it’s too much. One thing I have noticed is that on my iMac I get occasional “There is a script taking a long time to finish. Continue/Stop Script” errors, but never see these on the PC. I also don’t see them under IE/Win, the platform I am forced to use at work. I also get errors with Camino, but I’m not sure about Safari. I’ve gone into about:config, and changed dom.max_script_run_time from the default of 5 to 20, just to see if that makes a difference.