Reports of hardware failure seem to follow PlayStation 3 firmware updates as regularly as Summer follows Spring, but following the issues with firmware update 2.40 you can't be too careful. Multiple users over at the official PlayStation forums are reporting that their PS3 consoles are no longer reading discs following the 2.42 update last week. Some report that games play for several minutes after the update before the drive stops working, while others say the issue kicks in immediately. At least one forum-goer reported that performing a reset on his system fixed the issue, while others have tried with no luck.
It's pretty hard to get a good idea of just how many people are having the issue, what with the forum topic filled with "me toos" and claims that anyone reporting an issue is simply a troll. For the record, I just updated my system and have had no issues whatsoever. We've contacted Sony for comment on the issue, and will keep you all posted should further developments arise.
PS3 Udate 2.42 - System no longer reads my discs [PlayStation Forums]