I'm quite sure that the flight was dispathed to Seville from the beginning, it is almost impossible that it was a chain of small or big errors after takeoff.
One of the possible scenarios explaining how it happend could be that dispatch and ops support for this flight was done by Nordic ops from homebase, which is very often the way of doing wetlease operations. Normally the lessee (Spanair in this case) is just sending the daily plan for aircraft to lessor's (Nordic) operations office, and lessor's ops are preparing all docs, filing flight plans, sending crew brief etc. Someone in Nordic ops got a daily plan including BCN-SCQ-BCN and mistakenly read in his mind as "Barcelona-Seville-Barcelona". Next minute he started to prepare plogs/fpl/wx/etc for SVQ, because he remembered that he read Seville!
All above is pure speculation however based on my personal experience of doing wetlease business this could be quite close to the truth (we had a couple of close calls similar to this
.. Dhaka and Doha sound similar to each other over a bad phone line, and DC10F can easily make any of them from Athens...
