Chances are you guys setup your subscriber template with the "repeat greeting" set to 1 instead of the default 0. If you go pop open a subscriber's greeting page, all the way down at the bottom you'll see a setting for how many times to repeat the greeting and how many seconds to wait between repeats.
this setting is normally only used in special cases for audio text applications that expect input from the user so this defaults to 0. You can change it in bulk for subscribers already created using the BulkEdit utility.
