It is not allowed by PokerStars Terms of Conditions to run ICMIZER at the same time.
ICMIZER Suite can be used AFTER the game session and belongs to the category of software, officially authorized for use ONLY when the PokerStars client (PokerStars.exe) is closed.
PokerStars announced new rules of third-party software usage in August 2015, but they have not affected ICMIZER Suite.
You are personally responsible for knowing & obeying terms of conditions of your Poker room(s).
Everything is simple and straightforward:
You play at PokerStars with ICMIZER client closed.
You work on your game in ICMIZER Suite with closed PokerStars client.
Then you close ICMIZER, open PokerStars, and demonstrate everyone the new level of your game ;)