hello carlos, do you have a device with a fingerprint reader and authentec truesuite software (might be re-branded with a different name by your manufacturer)? if so please try updating it to the latest version or in case this doesn't work either you might have to contact the truesuite support directly.

in this thread we've already gone through the whole firefox troubleshooting procedure available and it looked like that no tweak or setting in firefox could cure the issue...

Hi @madperson. Thanks a lot for the reply. I did a quick search before creating this thread but couldn't find anything. Apparently I missed the one you linked.

I do have fingerprint reader software installed in my computer. By default it has also installed an extension in Firefox, which I disabled manually because I only use it to login to Windows.

I didn't bothered with the extensions because I thought that restarting Firefox in safe mode would automatically disable them or run without being affected by them. But it seems that's not the case.

Anyway, I couldn't seem to remove the extension without fully uninstalling the authentication software, so I decided to enable it again, just in case. And voilá! It looks like that besides being unable to uninstall it I also can't disable it, because somehow it messes up with Firefox. That said, I will just leave it enabled.

Thanks again @madperson. =)

P.S. The extension referred above is Simple Pass 6.0.100.252, from HP.

hey, glad you could solve the problem this way & thanks for reporting back with your findings ;-)