PCApex have a new guide up on how to recover from a coolant leak.

Even though your coolant may be more or less non-conductive when you bought it, over time it will pick up particles from your cooling system (dust, dirt, impurities, algae growth, and even microscopic copper/aluminum particles from your waterblocks) and the non-conductiveness becomes not so non-conductive over time. That is why it is so important to change your coolant on a regular basis. Over time it WILL become more conductive than when you first bought it. The longer you wait, the more conductive the coolant can become... If a leak occurs during a lapse in maintenance (when the coolant is most likely to be conductive) you have a higher chance of your components being damaged.

How to Clean Up After a Coolant Leak