[Zope] Help? ZGadflyDA product must be installed!

Hi, I've just installed Zope, and when, as the user (with manager authority) I created using the inituser account, I try to add the tutorial, I get the message: Error Type: Bad Request Error Value: The ZGadflyDA product must be installed! ZGadflyDA is in the Products list. It's in the right directory. Has the same permissions as other products. Can someone help me? Thanks, ==Leonard