FCP7 audio sync problem

Hi,

I am losing my mind with Final Cut Pro 7 and this audio that always goes out of sync.

I am editing some footage (ProRes 422, 48khz). And I have some audio which was recorded 4.1khz and I converted it to an aif file 4.8khz with Soundtrack Pro.

I went over a few tutorials and forums, and apparently putting everything at the same frame rate should solve the problem.

So right now I have both the video and the audio 48khz, and it still drifts.
The sequence setting is 48khz.

I really don't know why.

Any idea how to solve this problem?
What could still be wrong?