virtualbox.org

My VirtualBox does not see any USB devices, I cannot add any to the guest. Host Extension Pack is installed, guest extensions as well. USB 3.0 activated. Guest is Win 8.1 64.
Strange inconsistency:

myname@host-pc:~$ groups myname
myname: myname adm cdrom sudo dip plugdev lpadmin sambashare vboxusers

myname@host-pc:~$ id
uid=1000(myname) gid=1000(myname) Gruppen=1000(myname),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),118(lpadmin),129(sambashare)

Looks like you didn't logout / relogin after adding your user account to the vboxusers group.
As the id command shows that group membership is not active in the current login session.

Sorry, had been as simple as you wrote. Strange is that I had added myuser to the vboxusers earlier, but after some reboots, it did still did not work.
Anyway, now it's up and running, thanks a lot.