Hi,
If this is a new clean installation my best guess is not all the files got uploaded to the hosted server. I would try uploading the ClientScript folder again and I would also be concerned whether other files also are missing. I recommend not uploading all the files at once.
If this is an upgrade installation my best guess is you kept your old Web.config and are missing FCKeditor settings or have incorrect ones that would be there if you got the new Web.config file.
Also if you are using a custom skin its possible something about your skin is messing things up. Try switching to one of the included skins if this is the case and see if the problem persists.
Hope it helps,
Joe