So, I looked the code over and I saw that it's still using the old 8 MHz SD card data rate used by MBI since 2009. While we updated the code to switch to MBI's 1 MHz data rate for the rev H mightyboard, the 8 MHz was still being used. (The code can build using either, it was building with the 8 MHz variant instead of the new 1 MHz variant.) I've fixed things to actually build with the 1 MHz variant and I will test it now and then upload a new revision in case you want to test again. If you send me an e-mail at d a n . n e w m a n @ m t b a l d y . u s, I'll let you know when I've uploaded it for testing.