Unable to upload sketches over Xbee

Hopefully not an interesting or complicated problem, but it's beyond me.

I'm using an Arduino Fio, two Xbee Series 1's, and the Xbee Explorer Dongle.

I was able to upload sketches wirelessly all weekend and this morning. For no apparent reason (nothing is connected to the Fio save the USB power supply), I can no longer communicate with the device. I've checked the Xbee settings and everything is still all in order - I'm using the settings specified on the Arduino website.

I have the right board and port selected as well.

The error I get is simply, "avrdude: stk500_recv(): programmer is not responding"

Any idea what the problem might be? I'm just trying the simple Blink program currently.

Edit: It works now. No idea why. To the best of my knowledge I didn't change anything, but maybe I just reset it enough times.

You have the USB cable plugged in, to power the FIO, and you are programming it wirelessly. I see.

No, I don't.

I apologize for assuming people would also infer that there was an Xbee plugged in.

I inferred that there was an XBee plugged in. I don't see the benefit of bypassing the wires that connects the PC to the serial port on the Arduino, in favor of the XBee to XBee transmission of data, when the wires are already there because their counterparts are providing the power.

Now, if you unplugged the USB cable, and powered the Arduino to be programmed from a battery or wall-wart, and programmed it wirelessly, that I would understand.