take a look at these articles.
Bluetooth: Unreliable wireless performance may occur when USB 3.0 external devices are close
Using USB 3 devices on Mac computers FAQ
I sometimes have difficulty with Wi-Fi or Bluetooth devices when USB 3 devices are attached to my computer. What could be wrong?
Some USB 3 devices, hard drives in particular, can generate radio frequency interference that can cause Wi-Fi and Bluetooth devices operating in the 2.4GHz band to have issues communicating with your computer. Do not place hard drives or other USB devices behind the rear of your Mac near at the hinge of your screen. The antennas for Wi-Fi and Bluetooth are located there, and USB 3 devices placed there may interfere with your wireless connections. See this white paper for more information.
This exact problem is happening to me too with a 2013 Air. When I use a USB3 hub, the wifi often stops working, in exactly the same way as yours - it still shows connected for a while, but no data flows. If you disconnect and try to reconnect, it will show a timeout error. An older USB2 hub doesn't cause the same problem.
I've had intermittent wifi problems with the machine without the USB3 hub plugged in, but nothing repeatable, and the Apple store have tested the hardware with no faults found. It's very annoying, you don't know when it's not going to work!
Not sure if you've found your solution yet. If not, I might have an answer for you.
I got my latest MacBook Pro just last week (running OS X Mavericks). WiFi working fine until last night. Since then I have had the exact problem you described: WiFi won't work when a USB drive is attached (but on the USB port on the left, not the right).
I called Apple Support. The guy had never come across this problem but suggested a hardware reset which seems to have solved the issue. There are two resets. I did both. Steps are as follows:
Shutdown computer, plug in the charger
Hold for 10 second
Let go: charger light should go from Amber–Green–Amber
Immediately after hitting startup button, hold down Command–Option–P–R until a second sound is heard
Log in as usual
Please let me know if it works for you.