It seems like I run into this sort of power problem once a month lately. I am not sure if these are more prevelant lately, due to utility demand and surcharges, or if it's just that my clients have everything else covered through their power conditioning. This is a particularly bad impulse - which was damaging a CT Scanner once a week or so. The cause: Utility Power Factor Capacitors (roll your mouse over the power disturbance chart).

Of course, the real reason I wanted to put this on the site was the nifty Java script "mouse roll over".