SOLVED.
One BIOS flash later and I'm able to install 6.2 from the CD. (Not 7.1 beta though, but that's probably beta strangeness).
Incidentally, the flash file and utility are available in a file which makes a bootable USB stick. Very useful if you need a bootable USB stick, for any purpose, and are having trouble working out how to make one.
The (Windows) utility is here:
http://support.fujitsu-siemens.com/d...8-10CC6DAE0D82