Only the plastic is melted? PCB still not inside? just in need of a new casing?
My copy of New Adventure Island does this. If I apply a little downward force to the card while its slotted it works just fine.I wedge a small piece of folded paper under the lip after the card is inserted to play.
I recommend you go here OGHUGO: http://16bitgamer.forumotion.ca/Odds are he can help you fix that hu-card right up. With 20 pounds of hot glue.