After a few days:
- I would like to confirm DrRacoon was right, the problem is caused by using the DevTerm without batteries
- Although installing the pt-devices package allows the menu bar to gets displayed without batteries - it also prevents the battery status indicator to be displayed, as Glbr_Hanson mentions in another thread (The battery/power indicator doesn't show up)
So I would advise readers of this thread not to install pt-devices as I recommended earlier. Just install batteries 