That was the only time I shattered a router bit, it was NASTY too! I was using one of those brass collar guides on the base, and when the bit shattered it blew out the side of the collar, and I was also hit in the stomach by something, must have been a piece of wood though, because it didn't go into me like a sharp chunk on carbide would have.
It was back in highschool and the shop teacher said I had taken too deep a pass, not sure how deep it was, anyway I asked and he said something like, "take only 1/8" at a time", or something to that effect, and it stuck in my heasd, so I mostly do 1/8", sometimes 3/16", but when I start to take deeper passes the router also moves alot slower through the material, and more woods chips are created that I have to stop and vacuum out.