Well, Frodo, at least ya know what the problem is... and ya have a dollar amount for the repair.
What usually causes this sort of discharge? Condensation? Refresh my memory: capacitors store an electrical charge, right? And it looks like me thing Frodo's capacitor discharged that stored electricity, nearly causing a fire. What other reasons might there be for a capacitor to fail like this? Or discharge at the wrong time? Can a capacitor be faulty by itself?
You electricians bear with me, it has been awhile since I dealt with capacitors... just wanna learn a bit more about 'em.