Maybe your xxxxxx.default folder is deleted.

Actually I managed to sort it by uninstalling and deleting all personal options (instead of carrying them over) and reinstalling. Not sure what the problem was but working now

Locate your profile directory. See if there is a file named 'parent.lock, if so, delete it. If this doesn't work, try rebooting your computer. Still doesn't work? Hold down the shift key when starting Firefox, this is safe_mode. If it starts ok then you may have an extension(s) that are causing the problem. Post back to let us know if anything fixed it or not.

Mine says the same error message except it does not say it is not responding , just open , but it wont let me open , it just gives the message every time i TRY to open it

This just started doing this today , but it has done it 3 times , i have also noticed that my mouse wont scroll sometimes , i will be on a webpage and its like the page is locked , but if i move the page by the slider on the right manually , then the mouse scroll works again , this also just started tonight , so i am guessing the 2 are related , and i get no other system errors , or anything i can find running in the background , when i do get it to allow me to open it again , the pages stop freezing , till the next time , then the next time i try to open Firefox , i get the error , so the mouse scroll freeze and the error must be related somehow