What Canon powershotSX20 IS camera card size

SOURCE: memory card error after inserting SDHC card on powershot A620

the a 620 only goes up to 2 gb no higher

SOURCE: Camera reading memory card error, cannot get it to work. Tried removeing the card and replacing batteries. Checked and it is not locked.

try formatting the card once on a pc and then plug it in your camera....if that does not help either, you'll have to try a different card.

SOURCE: memory card error, memory card locked. canon a470

Move the slide switch on the side of the card.

SOURCE: i have canon a480 digital camera

on the card itself there is a switch
push it to the other side and try again

SOURCE: Memory card error message

Cards are coming in different formats and it might be possible that you brought a card which is not suitable or functional with your camera. The other reason could be that we are having options to lock our memory card in digital camera and you might have taken out your earlier card without unlocking it. The system might be broken from inside and this could be a reason that you are still getting a message that memory card is locked. It seems possible based on problem you are sharing.