Dual-language or multiple-language keyboards are widely used in many parts of the world, where users need to type in more than one scripts. During use of such keyboards, ‘input mode errors’ often occur when the user types in one language mode while the keyboard layout is set to a different one. These errors, along with frequent switching between input modes, are a source of confusion and distraction. In this paper we report on a study of this condition among Greek-speaking dual language keyboard users and describe a tool for automatically detecting this kind of errors and dealing with them in the case of an English-Greek keyboard. We also investigate the effects of this input mode error correction tool on a group of typical users during a study that lasted several days.