The plugin is pretty nice, but some things need to be improved.
One of them, the way you add required JS/CSS for the edit ads page. At present you're adding to ALL admin pages, and this causes some conflicts with TinyMCE making it having weird behaviour.
I made a quick fix for this to only include required files in the edit ads page.
You can find modified files at Pastebin:
http://pastebin.com/amXvK0CV (look at wp125_add_admin_menu() function)
http://pastebin.com/9rz2b8En (look at the start of the file)
I hope you can include these fixes (or similar ones) in the next release.