Okay this seems to be a reoccurring bug for me:
Whenever I switch to another window on my computer and Terraria is still open (not minimized), when I switch back to the Terraria window, I cant use any swords/tools, or click anywhere on the screen to do anything. This continues until I either press the inventory button or move my character in any way, and after I do that, all is back to normal.
Edit: It works the same way in the menus before the game actually opens the world too. Also for some reason, when I'm unable to click in the menus after switching back to the Terraria window, when I press "E" (my button set to inventory), it acts like a "back" button, and brings me to the menu before the one I was on.
It seems as if my second experience with the inventory acting as a back button was intended in the update, since Escape is the original inventory button. On the "Characters" menu, when i pressed the moving around buttons (wasd), it moved the cursor through my character selection screen, as if it were acting as the cursor. One thing I did find when I discovered this, though, was that you can't go down through the characters using the S key past how far is originally shows with out using the scroll wheel on the mouse. there is no way to scroll through the entirety of the list if resolution is not large enough.