Yesterday a mate of mine blew the engine in his vectra, (1.8 16v ecotec). His water pump bearing failed catastrophically, causing the cam belt to go slack, the valves met the pistons etc etc. The alloy vanes from the pump met the housing and disappeared into the water passages in the block resultng in a completely scrap engine. Thiss happened on a well serviced 60000mile engine which is untuned and has seen little hard use.
I don't know if this is an isolated component flaw, or a potential design fault, but if you hear a faint ticking from your engine, get it checked and dont move it, this all happened in about 3mins and the engine is now being replaced.