I had the same problem after installing Editor Monkey and then disabling it again. But I managed to get the original TinyMCE Editor back(that one that comes with WordPress by default). As already mentioned earlier. You need to to select TWO options boxes to get the visiual rich editor back. One is at
“options > writing > user should use the visual rich editor by default”
and the other one is at
“users > personal options (at the bottom of users page) > use the visual rich editor when writing”
Also in Editor Monkey (if you have the plugin installed) you can select the option for deactivating the default editor. Maybe you should try to disable them first (but I guess deaktivating the whole plugin will do the trick also).
If it still isn’t working I can recommend the Editor Monkey plugin – it comes with a more advanced version of the TinyMCE editor.