Cannot edit content items?

While working with the demo version of SEF advance, I went to edit content items (both static and standard) and found the screen looked like the attached image. Has this been seen before?

I tried logging out / logging in, turning SEF Advance on and off, and the problem continued.

Then I uninstalled SEF Advance and reinstalled Artio SEF and the problem was fixed.

I am using WYSIWYGpro.

Has this ever happened?