InvTweaks issue (items drop when clicked in inventory)

[VideoBoy]

This isn't really a Tekkit bug, but InvTweaks. It also happens when I install InvTweaks on my normal Minecraft JAR. But, since all Tekkit users have InvTweaks, I thought some of you would know.

So the deal is, after a random amount of time from starting the game, I get a bug where every time I click on an item in my inventory it falls to the ground. This keeps happening and I have to restart the whole game. Pressing both shift keys at once doesn't help; this is not the vanilla stuck shift key bug. I don't want to mess up during a raid so I just disabled InvTweaks, but i miss the chest sorting. Can anybody help me?

Thanks! :)

[danidas]

If you hit alt it will do that and if you hit it again the issue will go away.

[Jargen]

I get this problem using just vanilla Tekkit. I fix it by going fullscreen (Pressing F11).

[Dragetis]

+1 Danidas.