Da Mecca wrote...
We don't need a damn excuse.
The excuse is, time passed and your looks changed.
Jeez. please no more stupid pointless deaths.
Mmm yes, to Da Mecca you listen! Seriously, there doesn't need to be a reason beyond ME1's 'database error, please fill in the forms Shep'.
Shepard's death and resurrection served an important plot purpose in ME2 (and I kinda hope there is reference to it at least in ME3) but there doesn't need to be an elaborate explanation as to why we can give our Shepard longer hair (confirmed new hair styles a while back yaaaay).
Plus I just love the idea of Shepard having to sit there filling out forms because they got erased by mistake "I hate paperwork damnit!"