I have the same problem, and it's the second time that it's happening to my mac in one year.
I got my MacBook last December. I had the entire keyboard panel replaced in July this year due to the crack which had eventually lead to a string detached from the lower right corder of the palm-rest. Of course the replacement was free because it was still within one year warranty. Now, only less than 6 months later, the same place is cracking again.
I do not believe that us, the owners, should be responsible for this seem to be a "normal" defect of the panel and have to renew our warranty to keep replacing the panel (hoping that this is the only defect that we will be confronting).
Hope Mac can give a better solution to this manufacturing problem. chrisjwang@hotmail.com