When clicking on the FF icon on my desktop the browser will not open. I get a WindowsXP error message: firefox.exe has encountered a problem & needs to close. firefox.exe isn't listed in task manager. FF was loading very slowly for a day or so prior to its not opening. I've been doing a little reading re possible causes & I do have SiteAdvisor. What exactly is FF safe mode? I'd like some direction on how to proceed. My level is newbie plus--I put FF together!