[Elecraft] K2 Software Problem?

[g3naq at geoffgrayer.f9.co.uk]

My K2/100 has suddenly stopped working. If it was an RF problem, I would have some idea where to start. But when I switch it on, 'ELEC" appears on the display, but there it stays. So what do I do next? 
Please don't tell me to look for dry joints, wire whiskers, bent IC pins, or similar - I am an experienced constructor, and have checked for all these! 
Geoff G3NAQ ex AE4PI, HB9APY, F0ZY