When having content under review, I can click on the collaboration discussion button to display all the collaboration messages in one modal window. This modal opens well, but when I close it, it doesn't release the focus and the underlying interface is still greyed and inactive.

Step to reproduce:
1. put some content in a workflow so that they appear for review on the dashboard.
2. On the dashboard, click on the workflow discussion button.
3. Look at the discussion
4. Try to close the model window