Thanks folks
Yes we did a software update last night, which is why the avatars for some people have gone - that's purely down to Invision, who make the software, and not something we anticipated or were warned might happen. Soz. The + at the top of the site is just one of the updates so that's part of the software too.
The adverts thing - there's a notice about that at the top of the site; basically we are waiting for the ad server people to respond and sort out their bad tags and switch off ads that I didn't;t ask for.