Code: https://github.com/Ugdhar/tileentitytest

 

When I right-click my block, the inventory pops and and all, but even just moving items in my player inventory (which is all I have added in this test so far) doesn't work right, items don't actually pick up, and other items will randomly move about the grid. I've done some googling, but haven't been able to find any answers, and most of the code samples I've seen look similar to what I have, so I'm sure it's something I've missed or am not implementing or even not understanding.

If anyone feels like taking a look and seeing what they can find, that'd be sweet. Thanks.

Well, in your BlockTestBlock you are canceling the action if world.isRemote check fails. So you are opening only your guicontainer, without actually opening the container itself.

Apart from that I do not see anything obviously wrong

Hah, thanks @V0idWa1k3r, not 100% sure but I think I threw that check in there with the thought "Gui. . .only on the client. . .", without realizing the server just opens the container. Got rid of that and it seems to work, thanks a ton!