try manually rebooting the MRX/AVM first:
Disconnect the power cord.
Press the front panel power button five times to drain any residual power.
Reconnect the power cord.
Power on the MRX/AVM.
If still no luck save your user settings then try:
To manually reset the MRX/AVM to factory condition: connect power, and press the front panel Menu and Main Power buttons at the same time. The unit should turn on. This process is useful if the MRX/AVM has become inoperable. However, the method described above wipes all user settings.