sorry for kick-in in another hykem thread but try this:
download SD formatter, backup all files from your SD ( microsd) card to PC and format with this options in SDFormatter:
Format type : FULL (overwrite), Format size adjustment : ON. after formatting copy your previously backup to SD
also i can suggest you to try another card reader if you use one.
ps i got 5.5.0 fw, but method with Sdformatter save me bunch of times with card troubles
Thanks, Durig/Maximilious! It turns out the micro SD I got off of ebay was a fake. I didn't know that was as common as it apparently is. I would have been pulling my hair out in frustration for a week. Anyway, I tried Mario Kart on a 16 GB Kodak SD card and it seems to be working as expected. Thanks again for the help!