I've just freshly installed Xubuntu 12.04. I was using the update manager installing all the recommended updates and it asked me to reboot when it was done. After rebooting back in Xubuntu 12.04, I cannot launch Synaptic from the XFCE menu (under System) I also cannot install or remove any programs in the Ubuntu Software Center. If I try install VLC Media player for example, I click "install" and on the left of the install button where it says "free" it quickly says installing, then back to free. It does nothing.
Synaptic does launch from this terminal code:
gksudo synaptic &
When it launches, the following appears in the terminal:  2540
But I want it working from the XFCE Menu.
Can anybody help? It's much appreciated.