I'm with TyroPicard.
This is not a computer problem. This is not an Airbus problem (it has happened on Boeing too; SQ B744 at Auckland in 2002).
I'd even go so far as to say it is not a mixed fleet flying problem.
This is a problem with crews not having a rule of thumb, or gross error check in their heads. To me, that shows a lack of awareness of your aircraft, and far too much reliance on automation (of all types).
Getting the figures done by someone else (load controllers, dispatchers etc) is not a solution, it is merely an attempt to shift the blame in the event of error (they are human too).
Get back to basics, and focus clearly on the task at hand.