So there is no way to choose the exact version you upgrade to?
It actually turned out to be AVG that caused the problems.
I could no longer establish a connection with the torrent site, which showed the same page as if I were offline. I first changed the DNS from automatic to Google's, but it didn't sort the problem (although it did allow me to enter PBs origin site, which my ISP is blocking). When I temporarily disabled AVG everything was roses, and stayed that way after I turned it back on after reloading the site.
It looks like the download speed of torrent files had been normal on the other torrent sites i occasionally use all along, so the problem was only that AVG delayed torrent downloads from my main site.