well ... if you really jsut bought this copy of bf2 and installed it with the key that was INSIDE the package, then you should appeal the ban because its been added in August 9, 2007 11:59 am.
I myself had to request a new CD key for my World in Conflict copy cause its already being used! such things happen, jsut contact punkbuster or EA.
probably someone used a keygenerator and got banned with just your key unfortunatley, its all possible.
good luck
edit:
this is the account with which your GUID was banned:
http://spieler-daten.de/bf2_stats/koukis-ch
if its familiar to you ... well i dont know, but since the accont seems to be greek and you are from lithuania it doesnt seem so...