Sony announced Tuesday that it has isolated a manufacturing problem in the molding and coating of the PSPs outer shell, where excess untrimmed resin may be responsible for the square button's catch and hold. The problem, which Sony claims affected only 0.6% of the initial 510,000 units shipped in 2004, has been resolved and none of the newer units made from the start of the new year on should be affected. In addition, Sony has instituted a return and replacement procedure for anyone with a defective unit.
http://www.playstation.jp/info/qa.php?pid=&cid=480&sid=1
http://www.playstation.jp/info/qa.php?pid=&cid=480&sid=1