UPDATE:
Removing all *flightgear* packages and anything related/depending on them, solved this problem.
The upgrade 12.04.3 to 14.04 did work, in 1 go.
UPDATE:
Removing all *flightgear* packages and anything related/depending on them, solved this problem.
The upgrade 12.04.3 to 14.04 did work, in 1 go.