What would cause my c106 rectifier to melt down on an arduino 5v pro (?)

I had left one of my arduinos running over the last several days, and when i went to work on it today, i noticed that the masking tape / poor choice of insulation i and used to wrap it with caught fire at some point, and the c106 part of the arduino was melted down....

My question is, what caused this? Do those things get really hot, hot enough to catch the masking tape on fire (and thus damage the board) or, did the masking tape catch fire from another source on the board, and damage the rectifier?

classic chicken or the egg.

EDIT: I think it might actually be a capacitor. Its right next to the vcc, raw, and gnd pins on the side...

I think that is probably the 10uF capacitor shown as C19 on the schematic:

It is acting as a filter capacitor on the incoming power. Sounds like the capacitor was faulty or your power has way too much much ripple.