Please consider turning on send info to Mozilla from within Firefox before posting I have no information on your extensions. You give a description so general that it is no help what so ever. What color or colors are the shield ? What programs are you running that could cause this Shield, a antivirus program a ???? Is it a blue and yellow shield ? Did you just recently install something that may of caused this ? Probably Microsoft UAC (User Account Control icon) So it probably been disabled by UAC as it wants Administrator Privileges to run. Suggest right click on the Desktop Icon and then Properties then the Compatibility Tab and untick run as Administrator. You will need to go to C:\Program Files\Mozilla Firefox and find the Firefox.exe file there and do the same. Right Click, Properties, Untick Run As Administrator. If still having issues after rebooting please try : Create a new profile as a test to check if your current profile is causing the problem. *https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles *http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over the problem. Never work with original files. *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data *https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox Please let us know if this solved your issue or if need further assistance.