I grepped (searched) every single file in the Arduino 1.0.1 software download and the only results were .o files that contained __vector_7
Then I checked out line 523 in Tone.cpp and found the definition for an ISR called ISR(TIMER2_COMPA_vect)
grepping Tone.cpp again I found
#define TIMER2_COMPA_vect TIMER2_COMP_vect
grepping all files for TIMER2_COMP_vect resulted in 23 files with names like iom???.h that contained
#define TIMER2_COMP_vect _VECTOR(#)
where # = 3, 4, 9, and 10. But there were no 7's.
Switching tactics I googled Tone.cpp:523: multiple definition of `__vector_7'
This post in the forums might contain your solution if you are not using interrupts with the Ping sensor. http://arduino.cc/forum/index.php/topic,106043.msg960630.html#msg960630