Wasn't sure where to post this, but here goes. I just bought a refurb 2011 imac 21.5, and my browsing slows to a crawl randomly. SpeedTest always shows a steady 5.5 Mbps down, but websites load slowly or not at all. I'm connected in a back bedroom via Wifi and a Motorola surfboard router about 15 feet away through two walls. My iPhone and iPad's speeds are always fine. Any ideas?