Welcome to the forums.
Is the chord you're hearing part of a backing you've created? If so, there are a few possible things that could be causing this...
1. Did you regenerate the backing after deleting the chord? The change isn't registered until regeneration is completed.
2. Are any tracks frozen? If so then unfreeze the track and re-generate the backing.
3. Did you render the backing to an audio file (wav or mp3) before deleting the chord? If this is the case, it could be that the audio file is playing along with backing track. To check this, have a look under the "Audio" menu and, if necessary, kill the audio.
Regards,
Noel