I'm running Firefox 18.0.1 in Mac 10.8.2, but I've had this problem in other versions too. I need FF to run in 32-bit mode, because I often use Google Voice, which requires that. I've already gone to the information window for the application and checked the box that says "Open in 32-bit mode." Seems like that should solve the problem. But it doesn't. Every time I open FF and log in to Gmail, I get a message saying it uses plug-ins that can only run in 32-bit mode, and asking if I want to restart in 32-bit mode. If I just want to check my email it's fine, but if I want to use Google Voice I have to restart the browser. That's annoying, given that there already is a setting for starting in 32-bit mode, and that I've already selected it. Is that setting non-functional, or is there some way to make it actually work?