Symptoms
Clicking on a form’s rule does not show anything but an empty Rule Designer wizard
Diagnoses
This was due to the size and complexity of the form. The number of states present contributed to this.
Resolution
Simplifying the form by cutting down the number of states resolves this.
There is a documentation available which points out the best practices when it comes to designing forms: http://help.k2.com/k2ls-qrs022.aspx.