Hello! I'm trying to use Digital Persona u.are.u 4000B in Ubuntu with the libfprint. But when I run the example enroll program, it returns:

uru4000:error [dev_init] interface claim failed 
fp:error [fp_dev_open] device initialisation failed, driver=uru4000
In some forums, they says that the following must solve this problem:

sudo usermod -a -G plugdev $USER
groups | grep plugdev # Make sure there is output from this
sudo chgrp -R plugdev /dev/bus/usb/
But, the error remains the same.

Note: I'm using Ubuntu 11.04 32 bits