hmmm .. All you should have to do is install it and let it auto configure, I set my bit rate to 192, but in anycase just installing and letting it autoconfigure should work. you don't need to disable vbr - auto configure will automatically do it ..
I knoticed from your pic that you have the max bit rate selected, that is more than likely what your prob is .. trying uninstalling it, completely - Remove it from the registry and delete the program file - Then reinstall it, make sure auto configure is selected, then when it's done, check the settings and see if the max bit rate is still selected, it will say 224 but you should'nt be able to change it ..