Audio falls out of sync in Final Cut Pro X

So here's my situation. I notice that when I exported my video that the audio that was attached to the video clip fell out of sync when I added some of the royalty free music that came with Soundtrack Pro, the .caf files. While I am editing, obviously you frequently playback your video to check how smoothly it flows. Well, if I start playback from the beginning of the timeline the dialog is out of sync when the music is playing underneath, but if i stop playback and resume then it is back in sync. I am editing a short video it has 3 clips from an Sony AVCHD cam totaling 1 minute, there is (1) 3 second slug, followed by a cross dissolve that goes got into the first clip. Once the playhead reaches the 2nd clip and the 3rd, the audio is synced fine. The first clip was added to Audition so I could pick the best one as well as I tried adjusting the playback settings from proxy to high quality and still I experience the same thing. I am running a 17"MBP 2.2ghz Quad core, 8gb of ram and 7200rpm hard drive with a 1 gb video card. Does anyone have any other suggestions or is this a known issue?

Mac Pro 8-core 2.26 Nahlem, 16GB of RAM, ATI 4870HD, 4TB & 4TB RAID 0
17" MacBook Pro 2.2ghz quad core i7 8gb of ram 500gb 7200rpm HD 1gb video card

Hi Jason, the media is on the system drive. I don't have a portable drive thats fast enough to edit on with now.

Mac Pro 8-core 2.26 Nahlem, 16GB of RAM, ATI 4870HD, 4TB & 4TB RAID 0
17" MacBook Pro 2.2ghz quad core i7 8gb of ram 500gb 7200rpm HD 1gb video card

Yes I understand, but with all the enhancements to fcp 7 and X using proxy files I thought was the way to go on a MBP...which was why proxy compression was added right?

Mac Pro 8-core 2.26 Nahlem, 16GB of RAM, ATI 4870HD, 4TB & 4TB RAID 0
17" MacBook Pro 2.2ghz quad core i7 8gb of ram 500gb 7200rpm HD 1gb video card

The proxy codec was created to make editing on a portable much easier.

Mac Pro 8-core 2.26 Nahlem, 16GB of RAM, ATI 4870HD, 4TB & 4TB RAID 0
17" MacBook Pro 2.2ghz quad core i7 8gb of ram 500gb 7200rpm HD 1gb video card

I apologize when I read you original post I didn't noticed that it was the export that was the problem, plus you tried proxy. I should remember not to try to answer questions when I am home sick in bed (as I am now.)

This sounds very odd, I use those .caf audio files all the time from the Soundtrack Library. I would try a few things.

1 -make a new event and project, reimport your clips and see if you can recreate the problem.
2- convert the CAFs to AIFFs see if you can reproduce the issue there.
3- trash FCP X prefs, repair permissions on your startup drive (in Disk Utility)
3- if the above doesn't work, give Apple a call.

Again I apologize for my previous responses.

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T. Payton
OneCreative, Albuquerque

For those who've been kind enough to try to help with audio/video sync problems, I just had an eye-opening experience. I got my wife to check out a Vimeo clip I uploaded last night ... and it's perfectly in sync playing back on her PC. It's wildly out of sync on my iMac. Is it possible a marginal video card can wreak such havoc? If anyone is having a similar problem and wants to check out the clip for sync playing on your machine, try https://vimeo.com/37158320 Thanks, Bill

I'm having the same problem with the audio track recorded when I shot the video. I've captured video from my XHA1 and a Nikon P7000, and am having problems with audio/video falling out of sync. I've repeated capture, edit and export, and it comes and goes. At the moment, I'm unable to achieve sync with any of the files, even a 60-second clip from the P7000. This is making me crazy. I'm waiting to publish an indy music performance but can't until I can fix the sync. I've read and tinkered till I'm exhausted. Any help will very much appreciated.

Just did so to make sure. I've repeated all this so often I begin to doubt what I remember. The original media I just opened in QT is in sync. I may give it another go rendering in FCPX tomorrow to see what happens. What's more maddening is most of what I see on YouTube is also out of sync. I found a Google discussion group where a workaround was issued to try to correct that. Seems if it's not one thing, it's another. Thanks for the response. I remember when a quick tug on the film guide in my CP-16 ensured the correct frame count between shutter and audio record head was all it took. Analog video from my trusty Betacam never failed. It's a brave new world, and I'm a tired old fart.

My sync problem appears to have broadened. I loaded an .mov file from my Nikon P7000 last night. Played fine, all in sync. I trimmed it, no editing, saved it from QT 10.0 as an H.264, 5 mbits files, HD720p, and no editing. It's badly out of sync. (time-snip) All right, this may help somebody who's a Mac architect tell me what to do. I just played the original, unaltered file on QT, and it's way out of sync now. Tried VLC, the same.This is beginning to sound more like a computer problem. Does anyone have any suggestions short of buying a new iMac? This is what I have, and it has never appeared to struggle with either iMovie or FCPX.

Model Name: iMac
Model Identifier: iMac5,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.33 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 3 GB
Bus Speed: 667 MHz
Boot ROM Version: IM51.0090.B09
SMC Version (system): 1.9f4
Serial Number (system): QP6490J4VUW
Hardware UUID: 00000000-0000-1000-8000-0017F2C48233