MacOS – “USB device drawing too much power” error on startup with no devices connected

errormacospowerusb

Since upgrading to Lion, I get this error every time I start up:

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I've read the answers suggested here, but they seem to indicate that it's the presence of a second device that's causing the problem. The only USB device I have plugged in to my laptop is an external keyboard. I'm not sure how that's using too much power, but it's disabled my other USB ports.

Is there any way to fix this?

Best Answer

It could be a corrupt USB kernel extension. I'd try booting to Safe Mode:

  1. Turn off your Mac.
  2. Turn it back on and before you see the Apple logo on your screen, press and hold the Shift key until the Apple logo appears.
  3. A progress bar should appear below the Apple logo - during this time your Mac is performing a directory check and loads only necessary Apple kernel extensions (among other small things).

A feature of Safe Mode is that it reloads the kernel extensions from scratch, instead of from a cache file. It could be that during the Lion upgrade a kernel extension was damaged and has been cached afterwards.

Try the Safe Mode boot and see how it goes.

Good Luck!

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