My MBA 2010 started having network issue a few month ago. The symptom is: 1. sometime, the network speed drops to 0B/sec suddenly and all connection died, then comes back after a few sec. 2. When downloading large files, the initial download speed was great, 2MB/s, but sharply dropped to 20KB/s after a few sec. And never increase. I have another MacBook Pro on the same home network. Never had such issues with it. I also tried to download the same file from both machines at the same time or one after another. No matter which way, my MBP can consistently have 2MB/s speed, but my MBA only had 20K/s. I had this issue with MBA when it was running snow leopard. And I thought it may deal with OS. So just upgraded to Mountain Lion (clean install). But still the same issue. But when speedtesting with www.speedtest.net, MBA still works pretty good, 18mbps download, 4mbps upload. This really confuses me. I begin to suspect if my airport adapter is broken. Any help or suggestion will be appreciated.