There was a minor Inner Space update from 5389 to 5390 yesterday, but that update didn't change anything of significance to what you're describing.

Your issue sounds like 1 of 2 things.
1. a configuration issue with your window layout. if it might be this, I need to see your configuration in order to help you correct the problem (though running the window layout wizard or quick setup wizard would probably fix it)
2. a bug relating to Maximize. Games are supporting 3 windowed mode options lately. Windowed, Fullscreen Windowed, and Fullscreen. Fullscreen windowed may use Maximize, and it might work better to set it in Windowed mode.