When you have more than one user, you need to mount your data partition in both of the user's homes. With the 0755 permissions any user can read and write in that folder tree, but the visiting user can't start a new folder tree through your mount point.
Put a new mount point for your Data partition in the new user's home and the companion mounting line in fstab. Reboot and set the ownership and permissions through the new mount point to the new user. That should enable each user to create folder trees in the Data partition through their own mount points in their /home directories and also be able to read and write to the other users folder trees.
Ok... set up mount, fstab and chown ownership in each user's workspace...thanks!
Any ideas on the inability to enable the compiz settings?