Have you tried turning it (VirtualBox) off and on again?

I had a strange problem where USB devices were detected on the host system (Linux) but did not appear as available devices for a VirtualBox guest (XP). The strange thing was that I could use the devices normally on Linux, but they just didn't appear to the guests, not just XP but also a Debian guest.

I searched high and low for reports of the problem but nobody else seemed to have had it. And it was working before, although I was not sure if there was an intervening Linux kernel upgrade.

Finally in desperation I decided to reboot the system. Lo and behold, after that the devices became available to the guest. My best guess it that somehow the part of VirtualBox handling the USB forwarding got wedged. So give the old The IT Crowd advice a try.

VM in VirtualBox using unbound WiFi interface on host

I have a Linux host with 2 interfaces, a wired gigabit Ethernet and WiFi. Currently only the wired interface is connected. I wanted to experiment using WiFi interface by a VM guest in VirtualBox. There are various scenarios for this. I might want to test network routing by using the WiFi in conjunction with a smartphone offering tethering. Or access the Internet using from a VM on the desktop using the smartphone when the broadband connection is down.

The short answer is yes, this is eminently possible. The key points to take away are that, 1. the host has to configure the WiFi interface, i.e. load the appropriate driver and authenticate to the access point but not assign an IP address to it, and 2. the guest has to use bridging to access the host's WiFi interface. In fact it will appear to be a wired interface to the guest. All the usual IP configuration methods are available, static or DHCP, depending on what the access point allows. Also note that the MAC address seen by the gateway will be the MAC of the guest, not the MAC of the WiFi interface.