USB doesn't work anymore (after using Virtualbox guest additions?)

[Emubla]

Hi, my host is Ubuntu 16.04, and I run VirtualBox 5.2 with extention pack installed.
I don't know if it's just a coincidence, but everything was working fine 'till this morgning, when i try to edit resolution of a guest vm installing "VirtualBox Guest Additions".
The resolution now works well, but VirtualBox can't see anymore any device connected to my PC USB ports.
Can anyone help me?
Thanks.

[mpack]

The GAs have nothing to do with USB. Nothing more can be said without a VM log.

[Emubla]

The GAs have nothing to do with USB. Nothing more can be said without a VM log.

Where i can find th log?
I've found something in /home/user/VirtualBox VMs/vmname/Logs... Are those?

[mpack]

With the VM fully shut down, right click and "Show Log" in the GUI, save "VBox.log" (no other file) to a zip, and attach the zip here.

[Emubla]

Ok, there are 4 log files, this is the last one.

[socratis]

You didn't attach a log, please try again. Remember to ZIP the log first before uploading it (see the "Upload attachment" tab below the reply form).

[mpack]

Ok, there are 4 log files, this is the last one.

I told you the exact name of the log I wanted, so I'd prefer to see only that one.

[socratis]

mpack: That would involve something called "reading the reply"...

[Emubla]

Well... I'm sorry, i suppose this one is the right file.

[socratis]

Not to keep beating on a dead horse, but you still need to read carefully the instructions. Since you're new, I'm going to let this one slip , but in the future, attachments that are NOT ZIPPED are going to be removed:

save "VBox.log" (no other file) to a zip, and attach the zip

Remember to ZIP the log first before uploading it

[socratis]

00:00:00.514644 Guest OS type: 'Windows7_64'
00:00:00.631252 [/Devices/usb-xhci/] (level 2)

You have enabled USB3 for an operating system that doesn't have support for USB3. Did you install the additional drivers required? See: USB basics and troubleshooting, #6: Guest support.

BTW, you have 2 cores on your host, and you've assigned both to your VM. I would reduce the number of CPUs assigned to the guest down to 1.