I tried to PM a poster but when I clicked Send I was taken immediately to a Haven / Mumsnet page. I have no idea if my PM was sent or not. No message saying 'Your PM was sent' (or words to that effect) appeared. So I tried PMing someone else on the thread to see if it was a problem just with that poster, and saw my first PM message in the message box but my title erased. When I clicked my cursor at the end of my leftover message to backspace it out I was again taken to Haven / Mumsnet.
Also, the right and left margins on my screen are festooned with Haven ads where before they were white space.