Day before yesterday when booted my PC showed a dialogue box telling some applet is missing and it had two buttons 'dont delete' and 'delete', not sure what to do I clicked the close(X) button on the top left of the dialogue box.

Since then running programs are not showing in the bottom taskbar. All other things are working fine.

I use Ubuntu 12.04 LTS. if you need any other info let me know. I use Gnome (3.4.1) installed and I prefer it over the unity interface.

The screenshot of the pc which shows the lower taskbar i had and how the running programs were shown in it