I haven't used KDE in a long while, but this sounds a lot like similar problems in GNOME. Basically, you always wanted to keep at least one panel with the main menu on it. If you wiped it, things got ugly because you lost access to the main command menu completely. The only easy way to revert was to wipe your personal configuration directory (.kde), as mcveigh said. Very ugly "solution" if you had a lot of preferences set. If you don't want to do that, you might try creating another user, starting up KDE with him, and then running diff on the two .kde directories to try to figure out what you need. But not knowing anything about the KDE config files, I don't know how/if that would work.