Why does my gyro sensor returns -1 for the whole time

Yesterday I got my gyro sensor MPU 6050, and I used the program provided here Arduino Playground - MPU-6050 , and I downloaded onto my Arduino, at first, it went pretty well, the Gyro gives me some data, but later on, for some reason, all the values went down to -1, and I don't know why. Can someone provide me a solution