Can't access "Source" to edit text

I have installed CKEdit and played around a few times with until I decided to implement it in my client's new web site. When I initially tested the component, I also tested the switch between WISYWIG and HTML (Source) and it worked perfectly fine. But today, I have discovered that it no longer works. I switch to Source but when I click in the text zone, nothing happens. Can't edit anything! Any idea why? Is there a switch that was turned off somehow or is it related to license?