I've had this problem for a while now with my unibody MBP - when I connect USB peripherals or my external display via the mini displayport adapter, I get small sparks where the connector touches the laptop body around the port. This also causes pops on my speakers and also flashes on my external display (if it's already connected while I'm inserting a USB lead, for instance). I'm guessing this isn't normal?? But I can't seem to see what would be causing it. It happens both when AC powered or just running off battery, so I may be able to rule my electric mains out of the equation?? Any ideas???