arduino uno +mpu6050+hmc5883l problem

hello
i use mpu 6050 and try to connect it with nagnetometer and arduino uno to estimate the 3 euler angles
after run the example code the serial monitor give me this message

I2C write failed:2
what is this and how can eliminate this problem
if any one has another acceptable code can help
very thanks to this excellent community

http://forum.arduino.cc/index.php/topic,148850.0.html