[PROBLEM] Intermittent Wifi on RPi/Xbian

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Software
XBian version: 1.0 Beta 2
XBMC version: 12.2
Overclock settings: Default

Hardware
Power supply rating: From a Samsung phone.
RPi model: Model B
SD card size and make: SanDisk microSD 16GB inside a PNY microSD adapter
Network: Wireless, DHCP
Connected devices: Audio and Standard Video out, usb hub with Wifi dongle and wireless keyboard/mouse


I'm having trouble getting a consistent wifi connection on my Rpi/Xbian. It seems to connect fine while booting. The time is usually displayed correctly, but by the time it takes to check system info the connection is dropped and no IP is displayed. If I leave the system info screen up it will periodically connect, show an IP, and drop again.

I've had this RPi for over a year and recently upgraded from XBian Alpha 1 to Beta 2. I've had some problems before, but this is nearly constant.

Edit: Tried directly plugging in the dongle as in this thread. It had no effect.

Where do I start with troubleshooting this?