Originally Posted by
RumoredNow Unmount card, power down, remove card... Always the safest.
Insert card only when powered down, It will ask to be mounted, say yes.
Unmounting is really only necessary so the OS makes sure no programs are using any files from the card, because those programs may stop responding, or if any program is writing something to the card, that it waits for the process to finish so the written file doesn't get corrupted.
Unmouning before turning off is not needed, the OS does this by itself in that time that it takes since you hold the power off button until the phone actually turns off.
If you turn off a linux computer it will tell you all these things and more.
It's more likely that the printer did something funny to the card.
Stick the card into a PC (with adapter, usb reader) and try copying files to the PC (because otherwise you will lose data), and then format the card. Or format it in the phone itself. If the card fails, just take it back, they have 10 years warranty nowadays.