An external card reader (usb 3.0 enabled) is only like 8 bucks, free shipping, so im not terribly distraught about it. Its not like the microsd card is hard to insert/remove like it is in my phone, where i have to take off 2 layers of casing (defender series otterbox) and then the backing of the phone, and then make sure i dont get fingerprints on the screen or the inside of the case.
I know what happened, more or less, to cause the corruption. its not really a fiio problem, i think. Basically, i used windows to do the formatting the first time, then drag and dropped the files over. Everythign was fine at this point. Later, I did the firmware update. Everything was probably still fine at this point. Then I plugged it into my work laptop (also running win7 x64), which reported that there were problems with the microSD card. I hit "fix" because otherwise it wouldnt let me access the card. This is probably where things got screwy.
I'm pretty sure if i drag and drop things over now that nothing wrong should happen to the files, but im also certain that there is some disparity with the 32K allocation size and windows itself, because regardless of if bootice/guiformat utliity does the formatting or if the fiio firmware does the formatting, windows always reports that the volume is dirty and needs to do a "scan and fix" operation. That scan and fix operation is what screws everything up.
The solution (workaround) is to do the format, then plug in and get the dialog to do the scan/fix, and THEN do the file transfer.
However, if any other PC has a problem reading the card after that point, its a better idea to unplug the device than it is to try to read the data on the card.
When I first got my SD card (kingston 64gb) I had some probs getting it formatted (I think GUIformat was the only program that worked), and even then I did get some scan/fix warnings. I just ignored 'em cause I just formatted the card and everything worked fine for a while, then I started having transfer problems with Musicbee. Turns out my SD card reader drivers were REALLY out of date. Moral of the story I guess is, always update your drivers. Transfers have been fine since. (My laptop is kinda old - ~2009, so I'm not even entirely sure if the card reader is fully SDXC compliant in the first place).