Could be a power surge. Try getting a power bar with a surge protector for any "valuable" piece of electronics: TV, DVD, Computer etc.
If that helps you should probably get an electrician in to figure out why. Normal household wiring shouldn't normally surge enough to damage equipement (unless it's been hit by lightning or something equally sinister.)
You could also ask your neighbours to see if they have the same problems. Maybe the feed to the houses is "off".
Dave Montgomery, May 2004