You can start Firefox in Safe mode to check if your problem is caused by an extension or theme.
If starting in Safe-mode works then disable your extensions (Tools > Add-ons > Extensions) and re-enable them one by one until you find which one is causing it.
Close and restart Firefox after each change.
You can start Firefox in Safe mode to check if your problem is caused by an extension or theme.
If starting in Safe-mode works then disable your extensions (Tools > Add-ons > Extensions) and re-enable them one by one until you find which one is causing it.
Close and restart Firefox after each change.