I'm having a similar problem, but it is only with the Electroshock Grenade I've just researched. Dragging it onto the belt of a soldier in the inventory screen immediately causes the game to crash, although this only seems to happen with the top soldier in the list. I have managed to place the Electroshock Grenade in other soldiers' inventories successfully. All other grenade types seem to work fine - this bug has only just started happening.