After upgrading from Ubuntu 10.04 (lucid lynx) to Ubuntu 12.04 (precise pangolin) almost everything works fine, except launcher.
For most icons, left-click on the icon in the launcher does not trigger start of the application in question. Only starting the Dash and opening the Trash works. No other application can be started by left-click on its icon in the launcher.
My hardware: Toshiba Satego X200 laptop with nVidia GeForce 8700M GT.
Prior to upgrading I tested Ubuntu 12.04 from a bootable DVD. Prior to upgrading I de-installed almost all non-Canonical-supported packages, and afterwards re-installed via Ubuntu Software Center and Synaptic whatever I need.
As an attempt to solve the problem I tried the terminal command unity --reset-icons, however, this did not help.
During execution of unity --reset-icons a lot of messages were displayed in the terminal, which I quote below in part (omissions marked by [...]). I hope this gives a clue as to what is wrong.
$ unity --reset-icons
Checking if settings need to be migrated ...no
Checking if internal files need to be migrated ...no
Backend : gconf
Integration : true
Profile : unity
Adding plugins
Initializing core options...done
[...]
Initializing scale options...done
compiz (expo) - Warn: failed to bind image to texture
Initializing expo options...done
Initializing ezoom options...done
(compiz:2599): GConf-CRITICAL **: gconf_client_add_dir: assertion `gconf_valid_key (dirname, NULL)' failed
WARN 2013-02-03 16:05:13 unity.favorites FavoriteStoreGSettings.cpp:139 Unable to load GDesktopAppInfo for 'ubiquity-gtkui.desktop'
Initializing unityshell options...done
WARN 2013-02-03 16:05:14 unity.libindicator <unknown>:0 Desktop file '/usr/share/applications/libreoffice-writer.desktop' is using a deprecated format for its actions that will be dropped soon.
WARN 2013-02-03 16:05:14 unity.libindicator <unknown>:0 Desktop file '/usr/share/applications/libreoffice-calc.desktop' is using a deprecated format for its actions that will be dropped soon.
WARN 2013-02-03 16:05:14 unity.libindicator <unknown>:0 Desktop file '/usr/share/applications/libreoffice-impress.desktop' is using a deprecated format for its actions that will be dropped soon.
WARN 2013-02-03 16:05:14 unity.launcher Launcher.cpp:3088 Object registration failed. Won't get dynamic launcher addition.
ERROR 2013-02-03 16:05:14 unity.glib-gobject <unknown>:0 g_object_unref: assertion `G_IS_OBJECT (object)' failed
Setting Update "main_menu_key"
Setting Update "run_key"
