Thanks a lot for the feedback!
Well, the strange controls in the main menu is involuntary solution. We firstly tried to allow player to chose options by clicking on them, but our developer (me) got problems with making this mechanic (I tried to use raycast from mouse position, but it wasn't working well. If you ever had similar problem in Unity, I would appreciate, if you told me how you solved it).
The issue with entering nickname is very strange. We tested our game and nobody of our team had got faced such problem. Could you please give us more details about your problem?