I love this song- it's from the new moon soundtrack.
Play the Bb/G like this:  
e | ---3------------------- | 
B | ---3------------------- | 
G | ---3------------------- | 
D | ---3------------------- | 
A | ---1------------------- | 
E | ---1------------------- | 

Intro: ~ F  Bb  Bb/G  Cm  F#  F ~

Verse:

Bb         Bb/G
All of the astronauts
             Cm
Champagne in plastic cups
        F#          F       Bb
Waiting for the big hero to show.
Bb          Bb/G
Outside the door he stands
         Cm
His head in his hands
        F#           F
and his heart in his throat.

Chorus:

Eb          Bb
What can he tell them now?
Eb      C
Sorry I let you down
Eb       F            Bb
Sorry it wasn't quite true.
    Eb        Bb
But don't get hung up on it
Eb           C
Just soldier on with it.
    Eb             F            Bb
And good luck with shooting the moon.

Repeat for other verse and chorus.
Enjoy!