LE40R88BDX/XEU, not quite the usual cycling with relay clicking on startup as this one does start up but then locks up and power cycles after varying amounts of time. Checked the power supply, which appears to have been built with decent caps in this example, rather than the usual junk, anyway all the voltages 'scope clean as do all the ones I checked on the main board.
I have replaced the eeprom (24C256) and performed a factory reset which apparently allowed it to work faultlessly for an hour until it locked up watching Freeview and reverted to the original problem.
However, turning off the digital watch dogs in the options table does at least allow it to stay powered, albeit with Freeview (integrated digital tv for those not in the UK ;) ) not working.
As it appears to work in this state I'm going to leave it like it, as it's being used with a satellite box anyway and HDMI seems to work fine. Unless anyone has any ideas? I don't have access to a newer firmware file and for some reason this particular mainboard revision isn't appearing at the usual suspects, maybe it's just too old now :)