How do I place a multigroup in another multigroup? Is there any workaround to be able to place a multigroup inside another multigroup using CCK? 

This is what CCK tells me when I try to do it:


  You cannot place any kind of group inside a multigroup.
In Drupal 7, CCK Multigroup is succeeded by Field Collection, which can be used to nest collections within collections.

In Drupal 6 however, you already have your answer. You cannot place any kind of group inside a multigroup, due to the way the information is stored in the database.