USB error - Battery Life - Mid-2012 11inch MBA

The battery life on my mid 2012 (that I've had for almost a year), has dropped suddenly, and seems to correspond to the appearance of this alert message that appears after 20 seconds or so following every start up (whether plugged-in or on battery):

"Because a USB device was drawing too much power from your computer, one or more of your USB devices have been disabled.

To prevent damaging your computer, the USB device drawing too much power has been disabled. Other devices may have also been disabled. When you disconnect the device drawing too much power, your other USB devices will be enabled again."

This message started appearing about a week or so ago, and has never appeared before. The battery life has gone from 4 to 5 hours, down to about 2 hours or less.

I have no external USB devices plugged in. Nothiing plugged in at all in fact, other than the power cord when it runs too low.

Could this be internal damage or a short of some kind? (or maybe something wrong with the iSight camera?)

I've added no new software during this period. The only thing I can think of that would represent change is that the MBA rode in saddlebags on a motorcycle on a road with some bumps on it, but nothing terribly out of the ordinary. In fact, I bought this machine so that I'd have SSD that was less vulnerable than a traditional HD.

I also don't know which usb devices might have been disabled, as the keyboard, pad, and isight camera all function.

Any and all insights very much appreciated!

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Processor 1.7 GHz Intel Core i5

Memory 4 GB 1600 MHz DDR3

Graphics Intel HD Graphics 4000 384 MB

Software Mac OS X Lion 10.7.5 (11G63b)

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Apple Internal Keyboard / Trackpad:

Product ID: 0x0249

Vendor ID: 0x05ac (Apple Inc.)

Version: 2.19

Speed: Up to 12 Mb/sec

Manufacturer: Apple Inc.

Location ID: 0x1d182000 / 4

Current Available (mA): 500

Current Required (mA): 40

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BRCM20702 Hub:

Product ID: 0x4500

Vendor ID: 0x0a5c (Broadcom Corp.)

Version: 1.00

Speed: Up to 12 Mb/sec

Manufacturer: Apple Inc.

Location ID: 0x1d181000 / 5

Current Available (mA): 500

Current Required (mA): 94

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FaceTime HD Camera (Built-in):

Product ID: 0x8510

Vendor ID: 0x05ac (Apple Inc.)

Version: 80.25

Serial Number: DJHC56Z5QQDWC7C0

Speed: Up to 480 Mb/sec

Manufacturer: Apple Inc.

Location ID: 0x1a110000 / 3

Current Available (mA): 500

Current Required (mA): 500

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