I know others have had this problem but none of the posted answers proved workable. When I try to start Firefox, the browser does not open and I instead see the following message: "Your Firefox profile cannot be loaded. It may be missing or inaccessible." I am running Windows 8.1. This is what happened leading up to this problem. I was browsing normally when I got a pop-up message that said a threat had been detected and Mozilla had a security patch that I should download. Believing this to be malware phishing expedition, I closed the browser and restarted the computer without downloading anything. When I restarted the computer, everything was normal and I googled for info on what had just happened, to see if I really did need a security patch. One forum suggested that I may already have a virus/malware which caused the pop-up, and that I should deal with the possibility by refreshing Firefox. So, I refreshed Firefox, which seemed harmless enough. The refresh took a long time, so I finally closed the refresh window. Maybe I should have left the refresh window open but it was taking way too long -- after that is when my problem started with the error message. Since then, I uninstalled and reinstalled Firefox. I also deleted the profile folder in hopes this would force the creation of a new folder. Nothing has worked. Anyone have any suggestions to get Firefox running again? Thank you!