Panasonic DMR-ES10 stuck at "SELF CHECK"?

Loaded a DVD-RW disk intending to format it to use for recording. The DVD recorder refuses to unload the DVD and the display is stuck at "SELF CHECK".

Other symptoms:
Can switch it off by keeping the power button pressed for several seconds.
When powering back up, initially shows "HELLO", then sticks at "SELF CHECK".
Have tried disconnecting the power lead (for several minutes). It doesn't help - same symptoms when reconnected.

How can I get around this without opening the case?

Thanks for any help,
Geordie