[EasyRider]

Might be your config.ini has been corrupted

Check under the [hotkey Builder] section in the config.ini by opening it with notepad,
it is a list of shortcuts that can be used in the game.

I highlighted in red the shorcuts used for placing objects on the map,
check to make sure your shorcuts are the same as below.

This is the shorcut(hotkey builder) section from a config.ini of the stock 4.07 game,my backup config

[HotKey builder]
MouseLeft=objectMove
MouseRight=popupmenu
Enter=freeView
Shift MouseLeft=worldZoom
Alt MouseLeft=select+
Alt MouseRight=select-
Alt Ctrl=unselect
PageDown=change+
PageUp=change-
End=change++
Home=change--
Ctrl MouseLeft=insert+
Insert=insert+
NumPad-0=insert+
F=fill
Ctrl MouseRight=delete+
NumPad.=delete+
Delete=delete+
Backspace=cursor
Tab=cursor
F10=land
F11=onLand
NumPad-=normalLand
NumPad+=toLand
NumPad-5=resetAngles
NumPad-8=resetTangage90
NumPad-7=stepAzimut-5
NumPad-4=stepAzimut-15
NumPad-1=stepAzimut-30
NumPad-9=stepAzimut5
NumPad-6=stepAzimut15
NumPad-3=stepAzimut30