Q I am the proud owner of a new MacBook Pro Retina. However when I turn my HP LaserJet printer on, connected to the Mac’s left USB port, the keyboard and trackpad stop working, unless I restart with a USB mouse connected to the right USB port. Is this a problem with my 5 metre USB cable, or the computer?
A The long cable length almost certainly has nothing to do with it, although you should check whether using a different, high quality USB cable makes any difference.
Some strange USB problems vanish when peripherals are connected to a hub (or when those connected to a hub are plugged in directly to the Mac), so you should try a powered hub, both with power applied and without.
If that does not help, it is most likely to be a problem with the printer driver: let the App Store check properly for printer driver (and other) updates, ideally when your printer is powered up and connected.
It is also worth making an appointment at your nearest Genius Bar or Apple dealer and get them to run their hardware diagnostics on your Mac, to confirm that the USB ports are working properly.
Updated from the original, which was first published in MacUser volume 28 issue 24, 2012.