Canon 1DII malfunction - help please

[tikkathreebarrel]

Guys and gals, my 1DII has decided to malfunction, all of a sudden. It was working perfectly yesterday with no hint of any kind of problem intermittent or otherwise.
It stood, lensless but with the front cap fitted, on my desk overnight.
What does it do now? Frankly, nothing.

• It powers up on switch on but the switches/buttons/dials have any functionality.
• Removing/replacing lenses and cleaning the lens contact pins has no effect.
• The top and lower back displays illuminate.
• I've tried replacing memory cards and main battery several times, all to no avail.
• I've removed the CR2025 disc battery and refitted it which causes the main back screen to come up with the set date/time menu - which I can then set.
• I can't renew the disc battery until I can get to an open shop in a little while. (But if this battery was flat, why would refitting it trigger the set date/time function?)
• Here's the odd behaviour: having powered up, using the off/on 3-way switch has no apparent effect. Switch it off and the top and lower back screens stay live. Only removing the main battery causes these two screens to go blank.

I've now replaced the disc battery. No further forward: on boot-up I can change MODE but have no shutter actuation, functionality of the other controls or menus (other than set date/time after replacing the disc battery) so this looks more and more feel like a trip to the menders.

 

[Werecow]

Yep, sounds like a service is the only option left.