Overnight Gremins hit our website

Yesterday night, Gremlins hit our forum.

the post reply and starting box went missing, images disappeared and all kinds of strange things started happening. We then tried to upgrade to the latest software which looked to have solved some of the stuff - but that doesn't happen.

Sometimes when I go to the site it takes me to this website address

I tried turning off all of the addons and I now can't turn them back on as it's not...