What microSD-cards are you using, that are fully compatible with the TF300T?
I bought 2 cards recently, having issues with both of them. I just ordered a new card reader for my PC, hope that fixes the issues.
Card 1: Transcend 32GB Class 10 - Formatted to NTFS.
Issue: Fully working on PC. On the TF300T it is read only.
Card 2: Sandisk 64GB ultra class 10 (SDXC), formatted to NTFS
Issue: On PC, only visible when in SD-card adapter, write lock ON (switch option). When write lock is set to OFF, no card found. On the TF300T, I get read-only.
Will try to reformat the cards tomorrow when I get the card reader, hopefully that will solve the issues..
Samsung Galaxy Note 3 [SM-N9005]
Asus Transformer Pad TF300T 32GB
Samsung Galaxy Note 2 | Samsung Galaxy Nexus GSM | HTC Desire HD | HTC Legend | HTC Magic