The error 'The expression contains a circular reference' comes up when doing a 'Resolve' of the Test Data in the provided flow.
Release : 4.9
Component : CA Agile Requirements Designer
This exception error is normally shown when a test variable has a value based on another test variable and that other variable is based on the first variable.
However the error may also occur during a 'Resolve' if there are a large number of exceptions preceding this exception.
In that case, addressing the preceding exceptions should also address the circular reference exception.