When I suggested re-installing ubuntu-desktop, I meant *without* the DVD/CD.
Re-installing it should not affect any applications already installed as
there is no formatting. You use Synaptic (System, Adminstration), the
package manager.

Ubuntu-desktop is just a desktop environment that sits on top of the rest of
the installation. You can have as many desktop environments installed as you
want. Ubuntu uses Gnome, but you could install KDE or XFCE as well or even
replace Gnome. The applications for all desktop environments will be
available in the menu for each one. I only point this out to show that you
can remove ubuntu-desktop and re-install it without any damage.

Since you don't have a menu, you can use Alt+F2 and type sudo synaptic. Then
give your password and you can add or remove to your heart's content. Once
in Synaptic Search (not quick search) for ubuntu-desktop. It should have a
green box. Right click on it and choose Mark for Reinstallation. Then Click
on Apply and when done, it should re-build your menu.