instead of sudo xxxx, try sudo -s, and then type the command directly from the root shell and see if it behaves differently. things run via sudo can behave differently than from shell.
also, do you have a password or is your password blank? as of 10.5, sudo requires you to have a non-blank password. if you just hit return when it asks, it will just abort to a new prompt regardless of whether your password is blank or not. (this has proven to be very annoying for me, I had a thread going awhile ago asking if there was a workaround, but didn't find a workaround short of changing the password or using a different account that had a password)
You could also try it without sudo entirely, it will search any folder you can read. or you can login as root and just do the command without the need of sudo. this is all for testing purposes to find the issue, I'm not proposing this as a solution, just as troubleshooting / gathering information for us.
