From what I've read and experienced the NT OMAP3 SD boot process
is very finicky about the SDcard boot-partition's setup. Fortunately MiniTool Partition Wizard generally does very good job in creating a FAT32 boot-partition with the expected cylinder/sector geometry and alignment
, especially from scratch (i.e., on a SD card with no existing partition on it). So if an SD card repeatedly fails to boot it's best to delete all the partitions and start fresh.
Also, I have found it helps to first copy the MLO and u-boot files then the rest of the files, since MLO and u-boot are to be loaded first, and it appears that OMAP only scans the first few entries of the partition-table to look for these two files.
Finally it's worth noting that generally the lower rating (and also cheaper) class 4 SD cards are more suitable for running a ROM than the higher classes 6 and 10 cards (since the latter are optimized for large & sequential block read/write at the expense of random read/write). So if you happen to use a class 10 or 6 card and your apps frequently crash or freeze, consider switching to a lower class SD card.