breaker pops every time i turn on light?

my light in mybathroom worked for 8 years since ive lived here. a week ago it turned off and will not turn on. i have lighted switches in my bathroom, one for fart fan that still works, the other for regular light. this one does not work, and at first i thaught it was the switch because the light on faceplate was not on and the fart fan switch (right next to it) was lit up. so i replaced the switch, when i flipped on the power it blew the breaker. so i thaught it was the lighting fixture. i took that off the wall and did my testing. the wall has 120 v and lights up the faceplate on the light switch. but as soon as i flip the switch it pops again. what do i test next or am i wasting my time.

john in need
December 2009