Dialogue (and more) not displayed

At the beginning of act 2 there was a part with a dialogue between Homer and Lisa, which led to placement of some green square with four plantlike thingies. In my game, all the dialogue boxes in this game thread have been completely blank, the titles of the task pop ups were missing ("" has been finished) and when I clicked on the character icon on the left side, I could see the but not what they were actually doing (no name of task). I still don't know what this whole story line was about, also couldn't find it yet in the walkthrough.

Anyone else had this? Can you tell me, what the story was? I'm playing the German language version BTW.

Thanks!