Avisync problem

I'm trying to re-sync an avi file with a negative frame count (-10) and when avisync finishes the job, the sound is only made of quirks.
Thing is, if I play the file before avisync has finished the job (I launch vlc while avisync is still running), the sound is OK so I'm thinking of a file trailer issue (or header if he goes back to the start of the file to change things).
Anybody ran into a similar problem ?

duh, nvm that, avisync was trying to add a vbr trailer or w/e.

For those running in a similar problem before this thread dies : avisync might be build to support vbr files (avisync -h | grep vbr), you might want to deactivate it with '-b 0' if your file uses CBR. It seems that even if CBR is detected, letting support for VBR screws up...