OK its a bug. 100% Sure! Why? Because a friend of mine has the same problem.
http://bf2s.com/player/45852213/We played together at the time he got suddenly veteran heli badge. We both wondered and checked his stats.
BTW: He has NO skill in hacking or something like that.
I guess (!) it has something to do with lost data packages from gameserver to accountserver. The accountserver restores lost packages, but much later than they have lost the data.
So everybody who has the same prob, can enjoy the advantages of playtime (medals and so on), but must live with a horrible SPM.