So yeah, there's an advert covering half of my white ball so I can't put any right hand side on.. Erm thoughts? I know adverts are part of it when you've not purchased the premium membership but surely I shouldn't be hindered..

It may just be the size of the advert mate, i had that once before i had premium and it changed as soon as i logged out and back in.

Hey if it's not changed yet pedrera, message me please. I may be able to help.

i had same problem few days ago i simply made screen full size f11 then logged out and back in and it was gone .

This isn't an advert as they are bound to certain areas and are non intrusive in games. This sounds like Ad-Ware to me which is basically a form of malware (virus).

Is this happening on other websites too? Random adverts in places where they wouldn't normally be?

I suggest running a full system scan with MalwareBytes which is a very good program and is free too. http://download.cnet.com/Malwarebytes-Anti-Malware/3000-8022_4-10804572.html?part=dl-10804572&subj=dl&tag=button
Message me if you have anymore problems