ReadyNAS Duo RND2000 not booting - no disks detected

My ReadyNAS Duo was working fine yesterday - as far as I know, both disks were OK.

I beleive the firmware is up-to-date but has not changed recently.

I copied a large number of photos onto it and all seemed well initially but I did not check them as the process too a long time (perhaps longer than usual).

Later the device would not shut off as usual so I disconnected and tried to reboot.

Various patterns were observed and Raidar was unable to find it.

I have seen it with the power light on steady but no other lights.

I powered off and removed the disks to try one or two in the two slots.

The current sitiuation is that it will not detect disks. Raidar will now find it.

Currently the power light is flashing but I can turn it off by holding it down, as usual.

It will restart with no disks inserted and can then be discovered using raidar but with useful options greyed out.

The power light is flashing and the two LEDs are flashing in a pattern of 2 slow flashes followed by 3 fast ones.

Inserting a disk (or two) seems to have little effect.

Any ideas?

I was thinking about replacement as it's 6 years old and well out of warranty.

I'd rather like to be able to access the data!