Arduino Ethernet Board 3.3v & GND Shorted

I have just toasted a third Arduino Ethernet board (NOT shield), but I'm not sure how. The Ground and 3.3v are now connected. I don't have any idea why the first two were shorted. This most recent one occurred after plugging the board into a PoE switch and connecting it to my computer via USB. I doubt those two connections are what caused the short, as I've done that numerous times without any issues. Maybe it's my PoE switch. I was just wondering if anyone else has been having this issue, or similar ones with the Ethernet Board.