Wav file gets out of sync with sequence

Hello,

I have a 30min sequence that I sent the dialogue to an audio engineer for clean up as an OMF. He sent it back and it gets out of sync about the first 2 minutes or so. By the 30th minute the audio is out of sync about 47 frames.

I've tried multiple things, couple of observations: the WAV file's waveforms in the timeline show that all audio is in sync, yet when I playback in the timeline audio its out of sync. I even opened up the wav file on Quicktime player and timecodes from quicktime player and my video timeline do match, its only when i place the wav file in the timeline that it appears out of sync.

I've sent the whole sequence to Soundtrack Pro as a multitrack project. When I playback there it is in sync with the video!!! I export back and still same issue...

Editing on a Macbook Pro OS X 10.8.4 2.6GHZ Intel Core i7 on FCP 6.0.6.

The sequence settings: Apple ProRes HQ 25fps. Audio settings: 48 KHz, 16-bit, channel grouped.

Wave file (sent by audio engineer): 16bit 48.000KHz. Data Rate: 1528.21 kbits/s

Any help would be amazing!

Thanks,