There's a reproducible bug in Upgrade Complete 2 that causes a freeze if the player's "Game Music" stat is upgraded to 2 stars. The game will consistently freeze when a new level is started until "Game Music" is upgraded again to level 3.
If a player is stuck because of this, reload the game and purchase the third "Game Music" upgrade. If low on money, sell some parts and earn them back when the game is working.
I am playing on Chrome with the latest version of Flash, not sure if this occurs on other browsers.
