So, are we to gather that it is the card TYPE that is the issue ? Ie speed, or format type perhaps ?
If this is the case, you should be able to overwrite your original card with new map data - which seems to have failed when users tried this.
I feel its important to not get your hopes up, and trash a working card !
Its always baffles me why manufacturers NEED to over complicate things... the media card slot seems to reads most cards, so why add security to the map one ? After all this things are often "outed" to the masses within days ;-)
With the security removed you (Seat) could simply offer downloads from your site.... but of course, you wouldn't be making more more from that !