Just a WAG but it's been a while since I've 'messed' with an Airport Card...it's usually pretty hard to insert most cards/chips incorrectly and you only have two choices with a card...and you sound more than adequately capable of inserting the card the right way...but...but...since
both cards seem to cause the same problem...you might want to check that the inside of the socket does
not have any bent/broken/corroded contacts
and, just on the of chance, make sure you are inserting the cards correctly and fully.
"Repeatedly doing the same thing, while expecting different results, makes a man
unhealthy and
unwealthy...fast."