I’d try two or three things:
Assuming you have CS4 and not just Premiere Pro, right click on the audio track and choose edit in Soundbooth/Render and Replace. See if the entire track loads up in SB and if it does then just resave it and it will replace it on your timeline.
Load the clips into After Effects and export them and reload them into PPro. Sometimes those camera phone codecs are just flakey. You could try this with just AME as well.
Make sure you don’t have audio set up to quit outputting sound if the level clips too hard. One of those bite you in butt settings that serves a purpose AND gives you fits at that same time.