ok Caltoa and markT ; thank you for all..
i use exactly the sparkfun you talked : http://letsmakerobots.com/node/39234
when i test the scanner i2c it tell's me i2c device found at adress 0x68
at any time
for my ds1307rtc , and if i disconnctet it , it's tell's me the same for my mpu6050 :i2c device found at adress 0x68
if i connect both all together: same answer : i2c device found at adress 0x68
if i disconnect all of them : no i2c device found
is it a litle bit curious he find the same adress for both ??