da vinci ai0 0040 error code

this evening I got a dreaded 0040 error code on my da vinci. if you read the manual this code says it is an sd card error.
now the Ai0 supposedly does not have an sd card.
this is not correct, once you remove the back, there is a micro sd card in the middle of the board - this is behind the panel on the back fixed with 2 torx screws.
I removed this card, and reseated it - with no joy - still the error.
so I just swapped it out for another 4gb micro sd card (cheap one from a micro helicopter camera) and lo and behold my machine is back running.
on testing the card in an external card reader, it asks if I want to format the card - ie no file system is recognised
so if you get this error on an Ai0 that says it doesnt have a card - yes it does and its probably failed, I am led to believe it will accept up to a 32Gb card.
I hope this helps anyone who has this error find the cause.
note I did not have to do anything to the card, no files or formatting.