UML Collaboration Diagram Error

[dam]

I'm using Visio for Enterprise Architects SP1. In a UML
Collaboration diagram when I try to connect two Classifier
Roles via Association Role I keep getting the following
error message:

UMLE00080: Link1[AssociationRole] : [ClassifierRole -
WFR1] - The association roles connected to the classifier
role must match a subset of the associations connected to
the base classifier.

Thanks.