Can you try to restart the system and after POST enter the ESC key to enter the boot-loader. Then select NAS-Rescue_MODE to see if the system comes back up if not able to access shares then try with NAS-Single in the boot-loader. Then access the GUI to save your settings. Then download and ISO - burn onto CD then update. This will not erase your data. If you are still not able to save in the GUI your settings then you can regain access to your shares by going to the Resources tab and in Function create new share - uncheck the box "Create default path" there you can establish your shares again.