Lost 5th Gear While driving on the freeway

I was just driving along.. doing 110kmph on the freeway when 5th gear just jumped back into neutral.. If I try t o put it in 5th, it just grinds and won't take.. unless the car is stationary.

Just in a new house so funds are minimal to repair, so would like to have an idea of what it is before I look into it.

I can still drive the car.. just have to take it easy obviously.