QuoteYou obviously deleted the standard GUI but you still have the InventoryScreen function in your script... Either remove that function or reimport the standard GUI you deleted.
The InventoryScreen function pops up the built-in inventory gui. You can't delete that. The GUI that is present in the GUI pane of the editor looks like the built-in one, but is just a template to create your own.
As TK says, reimport sprites 1, 4, 2041, 2042 and 2043 or change existing ones to these numbers via right-click "Change sprite number..." in the Sprite manager.