"You cannot open the application 'iTunes' because another user has it open" error

If you are attempting to run iTunes interactively, for example, through a Remote Desktop Connection, please note that you cannot run two instances of iTunes at a time on the same computer:
If iHomeServer is running and has started iTunes, it will be displayed in the iTunes status area of the iHomeServer Management Console.  If iHomeServer is running iTunes then it is not possible to run iTunes interactively on the same computer.  We suggest you stop iTunes from the iHomeServer Management Console first, then perform any tasks within iTunes interactively.  When you have finished, close iTunes manually and restart iTunes via the iHomeServer Management Console.