could be a missing codec, could be a codec conflict or it could even be the AVI file itself. your best bet is to uninstall any codec packs if you have any installed and just install the codecs that you need
i used to hate going to weddings, all the old dears would poke me and say "your next", they stopped saying it after i did it to them at funerals -Chopper Reid-
Mick offers good advice; it is probably the AVI itself.
Whoever makes the backup AVI must synch it (or are you saying they playback synch'ed on other peoples PCs but not yours?)
Re-interleave the AVI using VirtualDub, or VDubMod, or NanDub.
Advance or retard the audio so it is synch'ed at the beginning of program.
If synch is lost as program progresses, adjust video framerate to achieve synch at end of program.
If it's synch'ed at beginning and end, but wanders in the middle, you're bunned and not much you can do.
Make sure both A & V set to 'direct stream copy'.
Preload 500ms, interleave every 10 frames for CBR or AC3. Best to interleave VBR every frame.
Hell, if you don't know what the audio is then just interleave every frame (file will be slightly bigger).
Job is not as hard as it sounds - I can re-interleave an AVI in about 40 seconds...
It is the trial-and-error that's time-consuming.
Write down exactly what you do, then check result.
Discard result if NFG, always work from original every time. Sooner (or later) you will get it as good as it gets - then pitch the original.
And do yourself a favour, write the new file to a different drive (or at least directory) so nothing overwrites ;-)
If you read from one hd and write to another, it is quicker (and, much easier on the drives).
Let us know how you get along...
Mick is that your photo?
i used to hate going to weddings, all the old dears would poke me and say "your next", they stopped saying it after i did it to them at funerals -Chopper Reid-