In case anyone else comes across this, it took me a while to find a
fix. I installed Ubuntu with ROS on a Rev. C4 board, and could not
get sudo or root access.
Here's a couple of solutions that worked for me:
1. The permissions on sudo were set wrong in the
http://people.mech.kuleuven.be/~kbuys/embsensor.html install. To fix,
after copying the beaglelinux files to the SD card, chmod 4755 on /usr/
bin/sudo and check for 440 on /etc/sudoers.
2. I'd recommend the first sol'n, but just in case, you can also
enable the root account without a password by removing the !* from the
root line in the etc/shadow file.