Items just dissapear :O

Everytime I go to my Inventory and i have like a Stack of something and i go with the cursor on it and throw it out with the "q" button.When I go to the point i was throwing at,there is not the full stack,just maybe the half.(And sometimes I lose evrthing)You can reproduce it by:
1.Take a stack of something
2.Move the cursor on it
3.Throw it out by holding "q"
4.Go to the place you threw it at
5.See it dissapeared
P.S I hope I was able to help you (Sorry for my bad English Grammar)