Well, yes the same problem that was originally identified by smokefree, and confirmed by tli and myself: That some older units including the nuvi 3xx series cannot use images of 2GiB and over, which is a quite well-known fact. The other external thread is dealing only with the fact that the OP was trying to get his 360 to see a full EU map on the SD when that image was well over 2GiB in size, and not at all dealing with your other problem of not being able to get an image file on the unit to work other than named gmapsupp.
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