We were creating a developer tool using three different languages: Delphi for the user-interface, C for the system-level stuff, and Synergy/DE for the glue. User requirements forced us to create our own message-box API. With all the hand-shaking between layers, someone confused the definitions for the bit values for what buttons to include on the message box. On the first run, we tried a delete confirmation. It came up "Delete 'filename'?" with the options, "Yes", "OK", and "Retry".