Hi,
I'm using kdenlive for some time. There's a bug, which occured in all the versions that I tried: Under some circumstances the "Align Audio to Reference" function segfaults. Maybe it depends on the video sizes, or format.
Currently I'm using the daily build Version 0.9.7 (rev. v0.9.6-134-g1f0072e), which also has the problem.
I found a solution, which seems to fix it:

$ diff audioCorrelation.cpp.sav audioCorrelation.cpp
38a39
>
51c52,54
< if (useFFT) {
---
> /* if (useFFT) { */
> if (false) {
>
55a59
>

Maybe somebody can investigate further, why the FFT segfaults under some circumstances and how to fix it.
Though for the moment, it seems to work good without using the FFT routine.