VLC cannot find audio codec MPEG 4 Audio (AAC) [aka mp4a]

Hi everybody.
I have a little problem with the latest version of VLC Portable.

I try to convert some videos with it but it tells me everytime that it cannot find audio codec mp4a (which is MPEG 4 Audio in the settings-window).

Sometimes I get a different message:

main error: Failed to create audio filter
stream_out_transcode error: Failed to find conversion filter for resampling
stream_out_transcode error: cannot create audio chain
main error: cannot create packetizer output (mp4a)

Does anybody know, how to solve this? A few researches show that it could be a problem with ffmpeg but I only found source codes?!