About three weeks ago I noticed a sudden drop in the responsiveness of my internet speeds. I should be getting up to 100mbps, but most speed tests I've run average between 1-5mbps, with temporary spikes up to 30 very rarely. My upload speeds appear to be normal. Comcast came out and looked at the modem, which they said was going up and down according to their diagnostics, so they gave us a new one. Now the other two computers in the house are getting good speeds over wifi, but my Mac Pro is still getting bad speeds. I'm not very far from the router itself, and I have full bars. The Network Diagnostics program detected no problems, even when I let it run continuously to catch intermittent problems. I reset chrome back to original settings and emptied the cache, tried safari, ran sophos, and (maybe against my better judgment) ran some clean up commands in Onyx, fixed permissions, and checked activity monitor to make sure no other tasks were eating the bandwidth. The router firmware is up to date and all my software is up to date. And with that, I'm stumped! Comcast tested all the wiring and determined that everything is working fine except for my machine. I would greatly appreciate any help you guys could suggest, you've been very helpful in the past! Thanks in advance!