I had a 32GB "made for Android" Sandisk card and had the same problem, albeit in a different Android device. Sandisk say it's a manufacturing issue according to info in this thread.
My solution was to buy a Samsung card :D
But I did try all ...
Has anybody tried Bluetooth tethering with this ROM?
I'm currently running TB with the Dorimanx kernel and it doesn't work, but I neglected to test with the kernel TB ships with so I'm not sure whether it's down to the ROM or the kernel. Had it...
Did anybody try ext3 or ext4 on an SD card with Xperia Tablet Z? Does it work?
Yes, I tried ext4 earlier but it refused to read it and made me reformat... :(