Have you checked your permission? Usually /dev/tty* are owned by the "uucp" group, so you should add your user to that group (hint: `man usermod` or `man gpasswd`). Another way is to give to all users Read/Write permission, with `chmod a+rw /dev/tty_Your_Device`, but it's not reccomended for security reasons.
Check also if you have read/write permissions on /var/lock.
Anyway, starting from 0.5_beta1, we have a Permission Wizard that will fix wrong permissions.