A couple of months ago, I would've voted "No failure despite 2 years of water cooling". But when I designed my new cooling system, bad luck struck more than once.
Failure #1: Mr. Murphy decided to pay a visit. When reattaching my Maze2, I accidently put the springs on the wrong side of the block, pushing it away from the core instead of towards it. Result: One extra crispy T-bird 1000 and total motherboard failure (probably due to extreme overloading of the voltage regulators when the CPU failed). It was probably time to upgrade anyway.
Failure #2: The reservoir (a plastic box of the type you would build electronics into) had a manufacturing flaw, causing a slow dripping leak. The drips reached my new NF7-S motherboard causing random lockups. After letting everything dry out, it worked perfectly.