About 6 months ago I modified a full tower and installed new MB, CPU, Ram, Video card, 320 HD DVD rom along with an ECO Coolit liquid cooling CPU cooler. It worked beautifully for 4 months but 2 weeks ago I started the PC one morning and it immediately shut down so I restarted it and it shut down again in a few seconds. I suspected CPU overheat as I had set the shutoff limit in the BIOS seup.
I took the side off the case and was horrified, there was water all over the inside of the case drenching the MB and video card especially. The liquid cooler seal failed and blew water all over everything.
Today I disassembled the pump and found the the "O" ring (double) on the discharge side of the pump has failed. I emailed the manufacture about the problem because it appears that the "O" rings themselves didn't fail but the plastic connector (female) had enlarged to the point that the "O" rings couldn't hold the pressure. The MB is cooked, the CPU and video card (after I dried it out) appears to be O.K.
I held a funeral for my MSI K9A2 Platinum board though.
Word of caution is DON'T trust water coolers.