Edit: After deactivating the "error message window addon", i now can see the real error message.
I will try to translater it and it says something like this:
"Gatherer has been blocked. The requested function is reserved to the Blizzard-UI. You can deactivate this Addon und reload the UI."
However, deavtivating Gatherer, the bot is drinking/eating again as it has done before. But nevertheless i had never had problems using Gatherer and the bot before the last update has been made.
Finally, i can live with this restriction, because Wrobot is awesome. I hope this bug reporting is still usefull for enhancing the bot.