You updated the extension and you are still using the old override syntax. Please go to your Typoscript setup an replace the old syntax like:
plugin.tx_grdslanguagemenu { settings { languageParamOverride { L1 = 5 L5 = 0 } } }
with the new syntax:
plugin.tx_grdslanguagemenu { settings { languageParamOverride { L1.lang = 5 L5.lang = 0 } } }
By the way: have a look to our manual an see our new features like the possibility to redirect a language extern or to an other pid.