[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] kragar00:
This may be the wrong place to ask this, and if it is, I apologize.

I also apologize for this being so long, but I wanted to include as much info as possible in case someone has a solution I haven't tried yet.

I have a Sandisk 32gb micro SD in my S3 (AT&T, rooted, running StockMOD 4.4 RC 2). The card worked perfectly fine before all of this started.

I ordered a new (generic) 64gb micro SD card through Amazon about a month ago. When I tried to copy my data to it, I got a 0x80070570 error, which seemed to point to a card defect. I sent it back, and finally got a replacement.

I unmounted the old card and put the replacement card in my S3. The new card didn't register in the phone at all.

I popped it out (the phone didn't recognize it, so I couldn't unmount it), put it in a USB card reader, and plugged it into my desktop (Windows 7 Home, 64 bit). The card said that it was formatted to FAT32. Since windows doesn't give you the ability to format to FAT32, I tried exFAT. I figured at the worst, when I put it in the phone, the phone would not recognize the file structure and give me the option to format it.

Well, a quick format didn't work (Windows said it was unable to complete it.) I tried a full format and when it got to the end, Windows said it couldn't complete that either. I put it back in my phone and it was recognized with a "blank card or unrecognized file system" error. It gave me the option to format it, so I did. After a maybe 2 seconds, the phone said it was checking the card for errors, then gave the "blank card" message again. I tried several times, but the same thing happened. I rebooted into recovery (CMW 6.0.4.7) and it seemed to show the card. I tried to format it there, but got the message "could not format /storage/sdcard1". I tried to mount it and got a "error mounting /storage/sdcard1" error.

I put the card back in the reader and my computer doesn't see anything there anymore. No drive letter. Nothing showing up in disk manager. I can't see it through diskpart's list volume or chkdsk (all run with admin privileges.) If I take the card out of the reader, the reader shows up as drive H (in all places). But once I put the card in, the drive disappears from everywhere.

So I figure I got another bum card. I put the old micro SD card back in my phone and it didn't see it. There's no message - the phone just doesn't recognize anything there. I rebooted, but still nothing. I booted into recovery and CMW doesn't see the old card, even though it worked perfectly fine up until this point. I tried wiping the cache and dalvik, but that didn't change anything. I booted without a card, inserted it, and the phone doesn't see it. I booted with the card in the phone, and it doesn't see it. I booted without a card, shut it down, inserted the cart, and rebooted, and that didn't work. The only thing I haven't tried yet is a factory rest. I put the old card in the reader and my computer doesn't see anything (just like the new one.) I tried disk manager, diskpart, chkdsk, etc. and it doesn't show up.

I tried 2 different card readers (1 USB, 1 internal) and neither reads either card. I tried 2 different micro SD to SD adapters, and neither one helps. I've tried reading the cards on 2 different computers, but neither sees either card. I found an old 2 gb micro SD card, plugged it into the USB adapter and it shows up in both computers fine. I tried both adapters and both work fine with the 2 gb. I also put the 2 gb in my phone, and it worked fine. So I think it's pretty safe to rule out an issue with the computer, the phone, the adapter, and the reader. Which leaves me with a card problem.

All of the solutions I've found online require that the computer actually assign a drive letter and see the card, even if it can't read it. I don't have that, so none of those work for me.

I get that the new card was probably a bum card. But why would my old card crap out all of a sudden? I had just taken a backup of what was on there, so it worked in the reader 30 minutes before I swapped out cards. I've inspected the contacts and they look fine to me. No scratches or crap on there.

Does anyone have any suggestions on how to get my 32 gb working again? Losing data isn't a problem, since I backed it up before I started this whole thing.

I've pretty much given up hope on the 64 gb at this point.