Why am I throwing items in FTB minecraft?

I am playing Feed the beast and I keep having a problem where I throw items I click on when I click on them. Any ideas as to why that happens?

Solution 1:

In most cases, this is a bug that occurs with the 'Not Enough Items' mod. Just to be sure, make sure that you are left-clicking and not right-clicking.
The problem can be fixed by disabling item drops in NEI and then turning them back on.

Solution 2:

This happens occassionally in may modpacks to which end the cause has not been really identified. Many other similar bugs include item dragging similar to shift clicking even though the shift key isnt held down.

One fix that I have been using is to change focus to a window that is not minecraft. Click elsewhere in another window then click back into minecraft. This 99.9% of the time fixes my problem.