i ovo pokusavam, ali ne mogu naci nista od ovog sto bi trebalo izbrisati??

Firefox Won't Start •• Disable IE in User Agent Switcher Extension


If Firefox doesn't start, the User Agent Switcher extension could be the problem. The problem may have been caused by leaving User Agent Switcher switched to IE. Open Firefox in safe mode and then switch the User Agent back to Firefox.

If disabling IE doesn't help:
Exit Firefox
Open Windows Explorer, and navigate to the *.slt folder
Delete the entire Cache folder
Delete the history.dat file
Delete the XUL.mfl file
Search for the parent.lock file, and if found, delete
(Firefox will rebuild the folder and files on restart.)
Check the Firewall to ensure Firefox has permission to access the Internet.

If you have installed any extensions recently:

Try starting Firefox in safe mode
If this works, try uninstalling (or just disabling) the extensions you've installed recently
Next: try starting Firefox in normal mode