marko,
Yeah, when I first received to bike back in '02, the whole key/lock mechanism was tight and kind of hard to work. But as the years rolled by, it's become a snap. I guess it's part of the "break-in period".
Try tilting the bars back and forth a little bit as use attempt to remove the key. That's what I do. And maybe shoot a little WD40 into the lock. I think I did that too when the bike was new.
Dwight