I'm having the same issue as @itsredberryy and pressing alt-F4 with the window active just prompts a new window that says "Are you sure you want to close the Sims 3 activation" with the only options being "OK" and "Cancel". Have uninstalled and reinstalled the game multiple times, repaired on the EA app, cleared cache, etc. No idea why this is happening.
I tried messing with DirectX and thought maybe the issue was with TinyUIFix but nothing I tried worked; eventually I found the solution on my own.
I simply typed in my username, pressed tab, typed in my password, and hit enter.
Basically logging in even though the window wasn't big enough to see it. After I logged in the first time, it did not ask me to again on subsequent launches.
