As I posted initially, one of the sites is drivecleaner.com. I have updated and cleaned my PC with SpyBot which found several problems. Whether that has fixed the problem there time will tell. I am now on my Mac and just signed into Pprune email and the other popup came up, url is
http://www.systemdoctor.com/download...ax=1&ex=1&mpt=[CACHEBUSTER]&aid=elserich_rdt&lid=mplx4. (Hmm, I see after posting part of that doesn't come up as html...cachebuster? sounds suspicious.)
The two formats are pretty well identical; warning, you are infected, you need blahblah, we will now check your system, and until you click OK there is no way of getting rid of it.
It doesn't happen every time, but it only ever happens on the Pprune email page.
Oh, I see, you wanted the url of the site where I get my email, Keef? It's
http://pprune.mail.everyone.net/emai...s/loginuser.pl
Now I'm racking my brain to remember whether I did actually get this popup on my work computer network and to be honest I can't be 100% sure. But my home PC's and Macs are all networked wirelessly.