Visualization plugins fail with .m4a files

[dave.haku]

In a nutshell:

Any visualization plug-in will not react to the music if the file being played is .m4a:

• The visualization comes up and renders idle animations, but does not move with the music or beats.
• The problem happens with .m4a files (CD playback, .mp3 files and Line-in work fine, I didn't try with more sources).
• All visualization plug-ins seem to fail (at least the three included with Winamp: AVS, MilkDrop and Tiny Fullscreen). The oscilloscope and spectrum analyzer in the skin work fine.

For a time I was noting that MilkDrop wouldn't react to the music, but only recently I got to narrow it down to .m4a/Visualization-Plugin. Is there hope in getting MilkDrop to work with my .m4a files? I already invested quite some time making .m4a files of my Music . I couldn't find references to this problem elsewhere.

I am using MilkDrop 2.2/Winamp 5.572/Win7-64bit/ATI Mobility Radeon HD 4670.