It is a permissions issue that is hard to fix. All but one USB device is greyed out. I am already a member of "vboxusers" I have already enabled and disabled USB support for the guest. I have already reinstalled the latest VBOx guest editions If running as root it all works fine Changing........

VBox/Virtualbox solution to NS_ERROR_CALL_FAILED error This is likely because you have 2D/3D acceleration enabled and your card doesn't support it. Eg. you switched video card drivers or video cards that did support it. The funny thing is that you CANNOT disable those options as they are "greyed" out in the VBox client GUI. The config file has to be manually changed and fixed with these options "accelerate3D="false" accelera........

The solution is simple but it's a wonder why VBOX doesn't address it directly? Perhaps newer versions will but you have to add your user to the "vboxusers" group and then login and logout and you'll see the devices you wanted but couldn't access are now available. The weird thing is that the grayed out issue doesn't happen with all devcies but one notable thing is the Apple iPhone especially in DFU or Recovery Mode which is an big issue for some people.........