Replying to Premiere Help?

I'm trying to put my movie together in Adobe Premiere CS3.  I have each segment as a different project.  I made my intro, and copy/pasted the first part in next to it.  Fine.  I went and copied the second part, but when I opened up the main file again, the audio waveforms of the FIRST PART were gone.  No audio.  The intro was fine, but that first part was fucked. 

How do I deal with this!  Someone please help me, its pissing me the fuck off.  I'll post this in Movie Maker Crew as well...