I have a week old clean install of 12.04.1. Everything seems normal.

I want to edit some .desktop files to add keywords so dash searches turn up what I want.

I found thousands of "desktop configuration files" in /usr/share/applications and more in ~/.local/share/applications. Mostly for stuff I'll never use.

Only a few have the ".desktop" suffix, mostly ones related to wine. Even ones I created myself with "Main Menu" do not.

I cannot edit any of them. If I try to open one it just starts the app. Tried as su... no go. Tried a few where I am the owner... no go.

Tried gksu gedit <filename>
and got a new empty file.

What the ????? Do I have to be in some kind of "ok2editLaunchers" group or something?

This keyword thing is pretty flaky. One suggestion was to use "Main Menu" to edit the launcher properties and put the desired keyword in Comments. Sometimes that works. Sometimes it doesn't.