I too just had this problem, except my card is brand new (only about 30 pictures total) and i'm using a Canon PowerShot SD850IS. I was at my kid's christmas play and we were able to take about 3 pictures then all of a sudden we got an error saying "memory card error" "Card locked" on the camera.
I've not contacted support yet, they are currently closed, I plan on contacting them tomorrow. I was just logging on here to see if anyone else has seen this error.
our old memory card works fine in the camera, I've tried to put the memory card into 3 different card readers on 2 different computers, none of which recognize the card.