I've just retried, and picked a range of different resolutions, both with, and without the 'R'. None of the stick. It always heads back to what looks like about 800x400 (sort of VGA ish, maybe it's actually 640x480)
I found some instructions elsewhere to edit /etc/X11/xorg.conf but I dont have one.
also some to edit /boot/evb.bin but I dont have that either.
Some background; This is a new board (and my first and only so far). I unpacked it, set it up, and booted it OK.
During the first boot it came up with the board-config.xh menu, and I selected something reasonable which I could read (1920x1080-60) and tested it. Enetered Y to confirm it and it rebooted and worked Ok for a while.
Within a few hours I had done an OS update (sudo apt-get update) and after that reboot it went back to this low res setting.
When I run Board-config.sh it now shows 1280x768-60 as the starred item (maybe this is the default?) but when I reboot goes back to something definitely less that 1280x768with the Circle-R of radioshack on the desktop taking up approx 1/2 the vertical screen.
Thanks for your help.