Hi Sane
This issue is perhaps one of the wages of viewing the Divx.Xvid formats on the conventional Blu ray/Dvd player.
I have come across a number of files which are out of sync when played through the divx formats. You are lucky that this issue arose only when you FF the transport. At times even if you don't FF, after a duration of say 45 mins the audio and video lose their sync, even in the normal 'play mode' which is not rectifiable.
I had come across an AVR which rectifies this issues, I don't remember the model, but it is probably Marantz / Onkyo which has the Audio sync retriever, with a calibration of (+/- 1 to 20 seconds) We can adjust the deferred A/v according to the lost or gained position. Try to google it.
Warm regards
JAYANT, Mumbai