In order to uninstall a possibly unwanted extension, please do the following:

1. From the Firefox window click the Firefox button at the top left and select Add-ons, or, if the Firefox button is not shown, click the Tools menu and click Add-ons.
2. Once the Add-on Manager has opened in a new tab, click the Extensions button on the left side of the window.
3. You should now see a list of your installed extensions on the right side together with buttons on the right side of each extension.
4. To remove an extension from Firefox, simply click the Remove button. You should see a message that informs you about the successful removal of the add-on.
5. Note that some add-ons require a Firefox restart to be removed completely. To perform a Firefox restart after the add-on removal, click the Restart now link in the message.

You can find further information about uninstalling extensions in the following articles:

Disable or remove Add-ons

Remove a toolbar that has taken over your Firefox search or home page

Hellon Nellus91! and thanks for the answer, but as i said i actually disabled manually all the extensions and plugins are set on never activate and the problem is still there. As i said everything runs fine in safe mode ( except flash videos as flash is desactivated ), all my plugins are also up to date! . Is there any other thing that safe mode disables that might cause the problem in "regular" mode?

Thanks again!

Hello armengolx7, turn off hardware acceleration and check firefox again (in safe mode hardware acceleration is disable).

thank you

Ideato, thanks for your help! That seems to be it!! I already enabled plugins and extensions and is working as expected.

Thanks indeed!

You are welcome