Unknown device-USB controller not recognized

I had an "unknown device" show up in devices and printers a couple days ago. It was also listed in device manager and said it was a USB controller. Everything worked and I've not added any new hardware. I have 2 partitions both with Windows 7 and the error showed in both. I've found that others were having the same issue, some needed drivers, some said cables needed replaced. Before I got serious with the troubleshooting, I read up a little and found a forum that said you should shut down then disconnect the power cord, wait a couple minutes then power up. Sometimes the motherboard needs to reboot and the devices will be reloaded or reassigned as they should be. It worked for me, it was an easy fix to an annoying problem. Since so many people have posted about this I thought I'd share this. If it helps, great. If not, it didn't cost much time or any money.

I can confirm this solution. I had the same problem and I turned off the computer, unplugged the power cable then plugged everything back in and restarted and the error message was gone. Finally!!! No more "Unknown USB Device" messages.

I can testify to that working too!! Instead of just rebooting I shut down and unplugged.
when I powered up it was fixed! go figure but I did notice that the unknown device must have been the USB Mass Storage Device which was corrupted. I'm thinking a funky flash drive was the cause.
:)

Even as old as this post is I had to sign up to say yes this worked for me too. I was skeptical but got tired of trying to figure out why I had unknown in my device manager. I shut down, unplugged and it worked! Thanks to the original poster.

Wow thanks this advice still works did exactly as original poster suggested and hey presto alls well again ..thanks

Thank you dmb219 - This has been driving me around the bend!! You have made me a very happy bunny!!!!!

Five year later this is still working. At least on a Lenovo T430U with Windows 7 Pro 64 bits. Join the forum just to say thanks.

Thanks a lot for the hint!

Welcome to the forum argmac. Many users don't realize that the computer retains 5 volt power even when switched off and usb lives in a 5 volt world. Many usb devices stay alive when the pc is powered off, some even continue screen output if you use a tiny lcd screen.

So - I joined just to say this fix worked for me as well - I hope it continues to work and that I don't actually have a 'real' problem.
Thought I would add my input to keep this search active and hopefully help some other lost soul with the same error