the "loop" setting must be the most important one.
"msdos" means the part table is written ON the storage dev, in the way a x86 would expect it to be. as far as I could find out this isn't the same for images (floppies, or VM "harddisks")
no offence to be meant, but if you don't remember to have changed this setting I simply assumed that you have not, since the partition table type is by default set to "msdos" (what in the most cases is the right way to do it) you would have to open the "extended" submenu and switch it there.
btw.
I know, I wouldn't have done it too, having no idea that the formatting has to be done in a different-than-usual way
I still don't know if this would actually help, I was only looking around for differences and hints, which might provide us with an OS-independent formatting solution. since parted recognizes this partition, I assume it should be (at least by the factory guys) to give us a parted script or something similar to to format the storage area w/o the need of reflashing