I have several Overo Airs.  I have a few of the older one that had 256MB RAM/flash, and one of the newer versions that has a faster processor and more RAM/flash (512MB).

I have a 32 GB SD card using the Sakoman build (r12).  For some reason, this SD card (I've also tried an 8GB SD) boots without issue on the older Overo Air, but doesn't boot all the time on the newer Overo Air.  If I do a reset on the board several times, it does eventually boot using the SD card and seems to work well once it's booted.  When I debug it using the serial USB and power it on, it spits out a few characters of garbage.  If I reset the board, it sometimes spits out garbage (and doesn't boot).  When it doesn't spit out garbage (it prints out the usual boot messages), it works fine.  It seems to reliably boot from NAND.  

Has anyone seen this and fixed it?  I think I have a fairly new MLO, but maybe there's a special MLO for the new Overo Air?