I had a similar issue with an Olympus OM4. It went in for repair but was never resolved. The batteries in my OM1-md last forever! I ended up doing the same remove the batteries after use. I can't remember the configuration, but if the LR44 are two and double stacked, you could use the Lithium equivalent.
https://www.batteryequivalents.com/ag13-sg13-lr1154-sr44-303-357-a76-lr44-battery-equivalents.html
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Have you tried using Google to find out what the error code actually means ? Very often, the first step in defining and correcting an error is to find out what has caused it.
Is this an SD card or SDHC card ? If so, have you inadvertently set the write-protect switch to 'ON' ?
To read it on your computer, you will need to get a USB card reader that will read your particular card, then connect this to your computer, which should treat the card as an extra drive.
You say the card has been in use for several years - it may just be corrupted or at the end of its useful life - I should consider replacing it soon.
Hi
If you look in the camera menu under the CARD tab you will find the option to format the card. This will wipe the data from the card.
We hope this helps.