Suddenly for no reason my game crashes when i try to assign a new item in my inventory to any quick key?, i can use the items that i have set now to the quick keys but as soon as i ether try to assign a key to another item or holding down a quick key for a longer time the game crashes to desktop!!

Any one that has a solution for this??

Loaded an older save and the issue was gone?

I think this is related to a stacking glitch in the inventory when it crashes when you are doing something with your inventory. for example, if it crashes when trying to Barter or assign Hot Keys. The way to solve this is to either load an earlier save like you did. Or, find a flat place on the floor, with no rugs or furniture near and drop every single thing in your inventory on the ground. Not in a container. Even the clothes you are wearing. Then pick everything up one by one and these problems tend to go away.

If it's the item glitch dumping the out and picking them up again never works for me..

You can leave them in containers and just take one out to use, which is fine most of the time...
However a sure way to do it, is to change the condintion of the item..

i.e Shoot a gun a few times untill you change its health, drop it equip the next do the same.. they then should stack normally again from now on.