You can download last firmware 2.85 here :
Just burning on CDRW 4x et updating RT6, wait 30'. Wait GPS reboot (display screen is ok) and ask new update, tell no , eject CD.
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Look this link :
Take Licence file GPS with "RT6 Activation map 2014-2.zip" on post 1 USB stick 4Gb.
Erase all files USB stick, no License file and copy all maps files new cartography 2014-2 post 1.
You can now updating RT6, USB stick is always OK when pluged into the car (thanks Licence file).
Each map are alone for update, you can to do only map you want.