username is missing in top panel in ubuntu 12.04 in Gnome Classic don't know why, i have tried to show it using dconf-tools but no success at all. How to show it back, i have tried to reset panels, but no success. Please help me.
Try Unity tweak tool or Ubuntu tweak, I realize these are primarily meant for Unity but I believe they work for the gnome fallback as well.
Ubuntu tweak can be found at getdeb, they should have a few versions available for various Ubuntu releases