hello 542merks,

can you please "Refresh Firefox"

1)on the URL Bar,type in - about:support 2)Click "Refresh Firefox"

Note: Refreshing firefox restores it to the default state,preserves your Bookmarks,Browsing history,Passwords,Cookies,auto-fill info etc. but removes Extensions and themes, website permissions, modified preferences, download history, plugin settings, toolbar customization etc.

Check and let us know.

@nowiz - Sorry I've already tried that, it didn't work.

I've noticed that it seems to be mainly video sharing websites, like youtube and dailymotion, that won't bookmark.

Places Maintenance {web link} Allows to run Maintenance tasks on the database that drives Places, the bookmarks and history module behind Firefox.

Open the Add-ons Manager. Locate the add-on and press the Options button. Select All of the tests. Then press Execute on the bottom.