in case you are using IR to have latest Vuforia SDK imported (Wikitude SDK's libExtensionVuforia.so must be copied to libs/armeabi, where also qualcomm's libQCAR.so is stored, you also need the QCAR.lib in your build-bath).
In case you are already up-to-date could you please send some more detailed error log.
Hani Hamadeh