Unable to create Test Plans in TFS web portal

I'm having problems creating and executing tests using TFS Test Manager and I'm hoping someone can help me sort them out.

I can create a Test Plan and associate it to an Iteration, and the add a new Test Case through the Test Plan associated to the same iteration. I've also tried creating a further test case through Parameters and associated it to the same iteration but not the Test Plan. Both the Test Plan Statuses have been set as ready. When I go back to the Test Plan, I have two problems as far as I can see:

1. The Test Cases created do not list under the Test Plan in the the left hand panel.

2. In the right hand panel, the menu bar with the buttons to execute tests displays for about half a second and is then replaced with an error message saying "No default test configuration is found". I suspect this is because of 1 above, but can't be sure.

I'm clearly configuring something incorrectly but cannot see what. Is anybody able to help me? I'll be greatly indebted to you if you can.