Interesting you should say that :)
I have gathered Slightly more accidental information to the above observations.
While, (after), removing the batteries from the remote control, (to be sure that it wasn't part of the equation) I jogged my desklamp... and the FLIRC generated a keypress.
So I turned the desklamp OFF, and the FLIRC generated a constant stream of <enter> and <up> keypresses, interspersed with occasional "-"s.
Depriving the device of light altogether, (Putting it in a cardboard box on a USB extension lead), stopped it... so it is behaving in this way in very low light conditions, but not No-Light conditions.
So then I decided to reprogram it. Start from scratch, so I unplugged it and replugged it, but it appeared completely inert, not responding to any input.
I had to reboot my PC to get it to be recognised, and then, the PC downloaded the bootloader/driver again. (Yes, it was always plugged into the same USB port).
Long story short, once the PC recognised it again, I used the "clear configuration" option to start afresh, and reprogrammed it, and it appears to work.
Turning lights on and off no longer has any effect on it.
I'll keep an eye on it.
<later>
OK. It now transpires that it responds to the FLIRC software, but after programming the keys, and exiting the FLIRC software, it does not detect any button presses on the remote and generate any input detectible by EventGhost, or on the Raspberry Pi Raspbmc.
It's possible that it's just a faulty item rather than a firmware bug, and the bahaviour with the lights was simply it's death throes.
are there any further tests I can reasonably do at home, or should I return it for disection?