Home Forums Tech Helproom Firefox will not run. Error message Forum Rules | Contact Forum Editor | Report a Post Firefox will not run. Error message Tycho 12:40 27 Dec 2014 Locked Answered I have been using FF for ages. Now it tells me: The application was unable to start correctly (0xc0000005). Click OK to close the application. What I have done so far is to scan my laptop (W7 with all the updates). No problems found using AVG free. I have uninstalled and reinstalled FF and get the same message. I am back to using Chrome now which seems to run without any issues. Any ideas? N spuds 13:38 27 Dec 2014 If you have CCleaner installed on your machine, then run a registry check with that, and see what happens. CCleaner free download click here Tycho 15:12 27 Dec 2014 Ccleaner downloaded and run. All seemed to go as it should but there is no change to FF. N Tycho 17:31 27 Dec 2014 Answer Thanks for your help, chaps. I resolved the ssue witha system restore. I had only created a resotre point yesterday so that seemd the most direct route back to a working version of Firefox. Nick This thread is now locked and can not be replied to.