I cant take out item from a same number slot as I have my backpack on my hotbar.
Ehm...

Example: I have my ProjectRed Backpack on slot #1 on my hotbar. I put an item inside the backpack on slot #1. When I will try to take the item from the slot #1 it won't let me (its acting like the item is locked in place). When I move my backpack to slot #2 on my hotbar I can take the item from the slot #1 in backpack, but can't take item from slot #2.

I hope this is understandable. :)

Using ProjectRed v4.2.2 build 19
Forge 9.11.1.965)
Minecraft 1.6.4.

Already fixed. Wait for next release.