Excel not responding after tab key pressed

I have a protected worksheet where all the unlocked fields are in rows that are hidden. The cursor has been positioned in A1, i.e. the cell is selected. If the tab key is pressed, the title bar shows ... Excel (Not Responding). This error does not resolve itself.

A message box has been displayed prior to this condition directing the user to another worksheet for data entry, however it is possible that they will hit the tab key and cause the "application lockup".


Is there a way to prevent this "application lockup" when the user performs this action?


p.s. version 2013