When I first started watercooling, it was in my freshman dorm room in college. My first setup was a bong cooler, eventually with a peltier and a Maze 2. One morning I got up and as I set my feet down they met wet carpet-I had flooded our entire room! It stunk of water wetter for weeks, so awful.
One day when it was starting to get hot in the springtime, my tubes were in the sunlight and the one going into the top of my bong bent, so I didn't have any flow. I got back to my dorm room to see my computer beeping furiously about the temperature, but condensation from my peltier's coldplate had already dripped on my Geforce 3. It never worked again.
Recently my Swiftech Storm leaked on my 6800 GT and fried it, I hadn't figured where the leak was when I installed my best friend's X800 XT as a backup card. It ended up leaking again while I was in the shower one day, and the leak killed the X800. I RMA'd the 6800 GT on a lifetime warranty from BFG and bought some non-conductive fluid. After a LAN party my system leaked again, but this time I didn't lose a card! Hurray for PC Ice!