I was in the Nether and while I was opening a chest near my Nether Portal, a Magma Cube pushed me into my Nether Portal (at exactly the same moment I was opening my chest). I did not get teleported back into the Overworld, but when I went to resume going through my chest (which was strangely still open, despite me not yet seeing its contents), the chest would not close, nor allow me to interact with it. I then broke the chest to collect its contents, but then found I could not access my inventory (pressing the button to open my inventory did nothing).

EDIT: I am unable to interact with ANYTHING that brings up a menu. I can still open doors/trapdoors, mine blocks, place blocks, sleep, etc, but cannot bring up my inventory, use a crafting table, cartographer table, etc...