[skaheadpunk]

Happened to mine, got it repaired under the warranty... and now it's happening again and for some stupid reason I didn't extend it. A guy in the mac shop near us said it was because of the two raised bits above the screen - close it too hard over and over and over again and it starts to damage the bottom.

And you can buy bits of the casing from ebay or Apple... but it'll cost ya! Ebay is like £40 for the inner top case (ie keyboard bit), more for black, more for the others. My Apple store said it would be about £100 from them.