game_text (apparently) doesn't work with a monster trigger_condition. Very strange.
BTW, I did some testing and your game hangup is most likely due to an infinite loop. You don't turn off or disable the trigger for your event.
However, there is an apparent bug with game_text. It will not display when the original trigger is from a monster trigger_condition!
I setup a headcrab to trigger some logic which then triggers an env_explo and a game_text. I tried 'death' and 'see player.' The explosion occurs but not the game text. However, when that same logic is triggered from a func_button instead of the monster death, the text appears and the explosion occurs.
I then setup the headcrab death logic to trigger some already tested camera logic which displays the camera location in text when the camera is triggered.
When the crab dies, the camera turns on okay but no text! Triggering the camera from a camera button displays the text properly.
Still playing around with it.
By the way, triggering an env_message does work.