update: I received my replacement cover today via fedex, free of charge from motorola by using the link posted above (though they first referred me to their store to buy it, I replied back saying they really should be giving it to me free since it's a manufacturer defect; they replied for me to give them my address and didn't commit to a free one, but hey the proof of the pudding is in the eating, and here the cover is in my hand, free)
anyhow, the manufacture date of my old one was 10/12/09, and the new one that got sent is 11/17/09; the prongs look identical between the two. Two major differences:
1) the black cushion is thicker, and less compressible (the equivalent of a business card trick)
2) the metal rectangle at the top that holds the cover in the phone is slightly more prominent (sticks out more)
the result: new door significantly more secure, takes more force to undo it. Well done motorola, though you should probably have apologized and sent a new door the FIRST time I asked, it's okay...my door is fixed. Good luck everyone, use that link!