Sandisk Ultra micro SDXC 64GB stuck in write protected or dirty volume

Memory Cards Mobile memory, professional cards and all other st
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It sounds like your card is faulty as according to Sandisk here, when a component on the card fails it switches to a read only mode:

http://forums.sandisk.com/t5/Mobile-memory-professional-cards/Sandisk-Ultra-64GB-can-t-be-formatted-or-permanently-altered/td-p/303089/page/3

I’m having exactly the same problems as you with a Sandisk 128GB micro SDXC card, Windows keeps claiming the card is showing errors but can’t correct them - I can’t write any files nor delete them or format the card so it seems it has failed. 

John