(1) The requested disk device (or remote network task) is not prepared to communicate with the V+ system. (2) A limited-access device like the terminal the pendant or a serial line is attached to a different program task. (3) You have tried to write into a pull-down window while it is displayed. (1) If the intended device is a system microfloppy disk drive make sure the diskette is correctly inserted and formatted. (2) If a limited-access device is specified ABORT and KILL the program task that has it attached or wait for the program task to release the device. If the intended device is on the network verify that the proper connections are made and that the remote system is operating correctly. (2) ABORT and KILL the program task that has the device attached or wait for the task to release the device. (3) The pull-down menu should not be modified with the FSET instruction while it is being displayed. A suitable time for modifying the pull-down menu is immediately after receiving a menu-selection event.