My GT-31 is now seeing my SD card as locked. The card has been fine for the last nn sessions. I tried writing to it one the computer and it worked fine. I've tested another card, it sees that as locked too. Anyone had this issue?
hmmm i seem to remember having this problem a while back but can't remember what it was, it was somthing small, i think it was just like some salt on the card or it wasn't in properly
Is it the GT 31 which is locked?
I inadvertently locked my GT11 last week and I couldn't even turn it off!
It's almost certainly the little sensor that detects the position of the card slider.
That sensor is buried deep within your GT-31, you'll have to pull it to bits to get to it.
Good luck 
I am having the same problem. Can be very frustrating when your waiting to hit the water.
I have had an improvement by blowing out with compressed air and updating the software seems to have helped but occasionally it still has to be re inserted 2 or 3 times before it works so if you find a solution I would be very interested!
