UE4 crashes when i hover mouse over Mode tab

I just downloaded UE4 and i"m new to it so please i need some help
When ever i dock a tab to the top of the Engine and move the mouse pointer past the Modes tab the engine crashes
and also when i tried to build lighting due the “Lighting needs to be rebuilt” error i was getting as well and it crashed in the process as well.

Please how do i fix these crashes?