I have discovered a funny thing;
Following mods are active in my game:
1- MP5K gun mod by "JDCollie"
2- Soviet PKM LMG mod by "begginfokillz"
3- Bolt action Rifle mod by "JDCollie"
My game is a steam game and they work quite fine along with 49 other mods (I guess, around 40 of them are active) and whenever I try to deactivate -any- single one of these mods, the geoscape in any game becomes unclickable. When I reactivate them problem disappears. It is the same for save games and a new game. In fact in a new game when the game asks for a new base placement, I can click on the text menu and close it but then I cannot click on the geoscape in any way. Even countries are not highlighted when mouse over.