I have been pulling my hair out over this. I have a Macbook Pro less than 5 feet from my new iMac and it's speed testing at nearly 20mbps. My iMac, on the other hand, is struggling to hit 5mbps. I have closed everything that I know to close. But it's had no effect. The iMac is a kind of software clone of an older computer that it replaced. I'm wondering if there might be some software I installed on the old computer somewhere along the way that might be causing me problems. Any ideas?