What is the frame rate of the ProRes footage?
What is the sample rate of the audio?
What are your sequence settings inside Premiere?
What export settings you did you use (Frame rate, Sample rate etc)
Have you watched it inside something other than Quicktime to check the lip sync?
Why are you converting the file?
Please provide all the media information for both your exported file and your original files, then we can try to provide with more accurate help.
I just encountered a similar audio sync issue on our windows system iwth Premiere CS6 6.0.3 exporting using the h.264 iphone 4s 960x540 30P preset resulted in audio synch problems. Source footage was 720P60 AVCHD.
This happened on all 4 sequences I exported to media encoder using the same settings.
I can't duplicate this. My exports always come out correct.
How are you playing back the files?
mpeg2streamclip and quicktime on windows 7. Have not tried on a mac yet.
Try not using anything QuickTime based for playback. Try VLC or KM Player instead.