Creo que también se puede utilizar la tecla Select del mando. Y me parece que sólo funciona con el nuevo firmware 1759.
Update: Me he equivocado es captura de la TV... por lo que dice pr2 necesitas un disco USB.
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With firmware 0.9.1759 it is possible to take a screenshot in jpg of the TV program you are watching.
Simply press the select key on your RCU when watching TV (this doesn't work when Menu are displayed).
And you will get a picture file in /DATA/hbd1/picture (for Premium with HDD installed), probably in /DATA/sda1/picture for Elite with USB stick.
Name is: cap = capture, chxx = the channel number in the favorite + date + time in U.S. format.