Andy, please try with a newer version of the mkfs.ubifs tool. For compilation instructions (because you will need the -F flag), check this link out: http://processors.wiki.ti.com/index.php/MTD_Utilities#MTD-Utils_Compilation
Here are also some details about calculating the sizes you will pass as arguments to the mkfs.ubifs tool: http://e2e.ti.com/support/arm/sitara_arm/f/791/p/268305/941327.aspx#941327
Best regards,
Miroslav
