Why does my Mac Pro (desktop) get half the the wireless Internet speed of my MacBook Air, on the same network? Both computers are using wifi over the same network (coming from wireless Verizon router using DSL).

Both computers are located in the same location (actually I have the MacBook Air sitting directly on top of the Mac Pro).

According to speedtest.net...

- Mac Pro gets 2.63 Mbps
- MacBook Air gets 6.20 Mbps

It's really annoying because the Mac Pro is my primary machine and slows down or times out on major sites (Twitter, NYT, even Mefi). Seems to come in waves - sometimes the Pro is perfectly zippy online, and other times it slows to a crawl.

I found other AskMeFi threads on speed - 1, 2, 3 - but still can't figure out why two machines with the same setup would get such different results.

If it helps, Mac Pro is running OSX Lion 10.7.2... while the MacBook Air is running 10.6.8. Otherwise I can't think of any significant differences between the two machines: same network, same distance from the router, same speedtest on the same browser.

Thanks for any help...