Win7 - Audio A52/AC3 not recognized

Win 7 64Bit Ultimate
avidemus 2.6.12 32bit
avidemus 2.6.12 64bit

Hello, i wanted to edit/save some downloaded videos with AC3 audio tracks which are ok when played on Windows Media Player, VLC or Windows Movie Maker. But no track is recognized inside avidemux.
All I get is this:

It happens only with "A52 aka AC3" audio tracks, all others are recognized.
I was so desparate I even installed K-Lite. Did not help.

Any ideas how I can get rid of this problem or where to start searching?

AviDemux does not use any external codecs, all it needs and uses is bundled with it.

It is probably a bug in the current version of AviDemux. Try an older version:
https://sourceforge.net/projects/avidemux/files/avidemux/

Hello,
thanks for your fast answer.
I just tried:
2.4
2.5.0
2.6.0
All with the same false result. None of them was able to detect/decode the audio track.
What else can we do about it? Are there any verbose or default settings?
I would really like to help with this.

It should just work. No special settings needed. Strange thing is that it does detect the correct bitrate and number of channels.

What kind of file is it?