Hi,
When I click on the Preview button and then again in the Design editor loses the cursor, I can write but can not see the cursor. I came to that as you click to a different place than the Iframe editor then it works and appears to back the cursor. I did also go to edit my own but it will not come. The error occurs in the latest Firefox, I checked the Opera is working properly. The same error is on your side in the demo.
aspx:
Config/radeditor.xml