After a recent upgrade, probably libusb, I'm able no more to use my usb devices although I'm in plugdev and usb groups. With root user these devices are accessed correctly. I've experienced this problem with my usbcamera and with my ZenExtra, mass storage usbkey works correctly. I found a workaround in forums ( http://forums.gentoo.org/viewtopic-p-3386425.html#3386425 ) which consists in putting a specific udev rule to set correct permissions. Of course before that upgrade all devices were accessed with normal user. [I] dev-libs/libusb (0.1.12): Userspace access to USB devices [I] sys-fs/udev (087-r1): Linux dynamic and persistent device naming support (aka userspace devfs) If other info are needed just ask
Probably related to bug 131756, try libusb 0.1.11
*** This bug has been marked as a duplicate of 131756 ***