i guess it is just one of those things. electrical items are prone to spikes and surges in the mains supply which weakens them over time or could fry them instantly.
fridges washing machines and next door using power tools etc switching on can all have an effect on your expensive hardware. at least it didn't take your motherboard etc. with it so you are lucky.
my advice is buy a surge protector to protect your equipment if you have not already done so. Belkin are good and very cheap click here and the best thing is when your surge protector blows just send it back to them and they will give you a new one for free whenever this happens. if you should be unlucky and your equipment is still damaged they will replace all your equipment connected to this up to a certain value. well worth the small outlay in my opinion.