I have had rev A MBA for 3+ years. Today I plugged in a externally powered blu-ray burner and had a warning along the line of "USB device trying to draw too much power and will be shut down". Since then, no USB devices will work off the USB port. I have tried: 1) Reset PRAM & VRAM 2) Reset SMC 3) Diagnostic tool test- won't boot into diagnostic test when holding D at boot and obviously can't boot of superdrive! I don't have another computer handy to do remote disk access for this. 4) Booting into safe-mode made no difference I am out of extended warranty so can't call Apple for help. Any suggestions welcome before I bite the bullet and take it to the genius bar!