As it seems that nobody has actually looked at the source to see what I need to improve on, I'll lay down some facts and specify exactly what the issue is:
This is a ModLoader mod, ported to Forge. All blocks and items are working.
The GUI for BlockDrill.java is not working
The GUI is called, but is quickly closed when the server is handed the ContainerDrill instance
The GUI, when the server is NOT handed the ContainerDrill (but null instead) will render perfectly (this indicates GuiDrill works), but grabbing items will grab the one to the right of it. It also doesn't save anything at all, since it isn't syncing with the server I presume.
Now, what I need to know is what could be causing the server to close the GUI so suddenly after opening, and how can I fix this?
EDIT: Got it working! I ended up rewriting my ContainerDrill class based on the wiki's tutorial! However, I'm still having troubles with syncing the inventory. If I try to grab any of the items out of the hopper, it vanishes as if it wasn't changed. But, when a user adds an item, it will stay. What would cause items to vanish when they are set by the mod and not a person?
Also, blocks set by my mod reset as well when the chunks are reloaded. Is there a proper way to sync blocks with the server too?