Did you try this? This was my problem using OH2 Beta4.
Device Permissions / Linux Device Locks
When OpenHAB is running as a non-root user (Linux/OSX) it is important to ensure it has write access not just to the PLM device, but to the os lock directory. Under openSUSE this is /run/lock and is managed by the lock group.
Example commands to grant OpenHAB access (adjust for your distribution):
usermod -a -G dialout openhab
usermod -a -G lock openhab
Insufficient access to the lock directory will result in OpenHAB failing to access the device, even if the device itself is writable.