virtualbox.org

Windows 7 64 bit host. Windows XP and Linux guests. Card reader Chieftec CRD-501 D
After recent upgrade of virtualbox the flash disk cardreader became crippled under host os Win 7. Either of the guest operating systems can access the card reader normally when usb is enabled. However, when the guests and vbox manager is not running, the usb-cardreader are visble in in the windows device manager as removable media (even without any media mounted). All 4 ports for different cards are marked as not usable. The usb-port is working as expected and has an assigned drive letter letter.
Despite marked as not usable in device manager, the micro-flash port is possible to use, but for some reason the normal size flash port does not work.
However, after starting either the XP or Linux guest the card reader is operating normally from within these guests. When the card reader is mounted within the guests, the post in the windows device manager for removable meda disappears and comes back as soon as the guest operating system is closed.

Any suggested solution to get the card reader working again?

VirtualBox VMs do not grab USB devices automatically, you must have configured a USB filter to grab the card reader. USB does not allow multiple hosts - when a VM grabs the card reader the host (and any previous VM) loses use of it. As you have discovered, the host PC is not expecting to lose this device and doesn't necessarily reacquire it when the VM is shut down.

To prevent this problem, delete the VM's USB filter.

If you want your VMs to access data on the card reader then I suggest mapping it to a shared folder, rather than yank ownership of a host device from the host.