Now I recall another thread from another forum in Hong Kong regarding Sandisk 64GB cards
http://www.hkepc.com/forum/viewthread.php?tid=1830406
In general, they seemed to have better luck with Class 6 cards than Class 10 ones.
Basically if someone were formatting their Sandisk 64GB cards with older card readers that did not even support SDXC to begin with, most likely those cards are "gone" for good and must be replaced under warranty.
In other words, that might have caused some irreversible damages to the flash memory chips while not much could be done by an end user afterwards. Definitely check the official web site of your card reader's manufacturer and confirm that SDXC cards are indeed supported. Preferably *BOTH* SDXC *AND* micro SDXC flavors are supported so there will be no surprises.
If your card reader were not the culprit, just try to format your card(s) again with the *official* SD Formatter 4.0 instead of something else:
https://www.sdcard.org/downloads/formatter_4/
Hopefully that will allow us to pick FAT32 for 64GB cards. If not, version 2.0.0.3 is still available at the moment:
https://eww.pavc.panasonic.co.jp/support/jp/sd/sdfv2003.exe
BTW, glad to know more fellow owners of TP here in Hong Kong. If only we could figure out how to get HDMV LPCM (from Blu-ray) working on TP. Still not getting anywhere with that one yet, even Colorfly C4 Pro kept throwing that "Play Error!" while both FFMpeg and eac3to gave me the same results so far. Somehow everything is OK with my laptop running Windows 8.