Almost certainly this is caused by a corrupted preferences file - all of the presets are stored there. If you have nothing special that you've created yourself, then the easiest way to restore all of the preferences to a 'vanilla' state is to restart Audition with the Shift key held down. If you want to be a bit more specific, then probably file to delete in Preferences is EffectPresets.xml.
Hey I tried the "vanilla" state startup.. but the same problem still occures on my version. Anny other suggestions?