I always find it fascinating how the smallest detail can bring an entire system to its knees. In this case, a simple player-made Black Ash bow will accomplish in Middle Earth (at least the Lord of the Rings Online version) what Sauron with all his host failed. From the technical support forum:

If you had this on your character, you crash on login. If it was in your vault, you crash when you try to access the vault. If you create this bow, you'll crash... The recipe has been temporarily disabled. And please, don't buy it or even try it on if you see one on the Auction House - curiosity killed the cat, and it'll crash your client, too.