Got mine working... it seems...
I would suggest the following sequence.
1. Install VirtualBox (I don't think it matters whether you add the repo or pull the rpm and install locally - as long as you don't mix the Open Source Edition with the PUEL stuff)
2. Make sure the user is part of the vboxusers group. This was somehow trickier than I anticipated. The user tool under System Settings sucks, so I used the usermod command from the command line. Then I checked it via system-config-users. Somehow I was NOT part of the vboxusers group. So - bottomline, you need to be part of <user_group> (Primary), vboxusers, wheel (if you chose "make Administator during setup of the account). Please double-check this as I had some anomalies here.
3. Download and save the Extension Pack. Remove previous versions (if any). Install from saved location.
5. Run VirtualBox. Create/Configure a guest
6. No more USB error.....