5big2 network assistant update cannot be stopped

My 5big2 runs without blinking lights but does not show in network or network assistant. Trying to update the assist.program through network capsule 2.2.10.1 first showed some progress but now cannot be stopped! Trying to download a newer firmware version failed as the website keeps telling me to check the s/n of my device.
I am completely stuck, as the 5 hd's contain work of several month which is practically lost! I am no computer freak just the "dau" so please if you feel you can help - use plain language!
Thanks
I am completely stuck, as the 5 hd's contain work of several month which is practically lost! I am no computer freak just the "dau" so please if you feel you can help - use plain language!
Thanks