kgrubeditor messed my system

today i wanted to try kgrubeditor for kde4 and when i did and typed my root pass it took a long time to response then ask agin for my root pass but when i typed it it said wrong pass

to cut it short it messed the whole system , but one the most important one was that it changed /bin/su mode and i had to log in as root in text mode and then chmod u+s /bin/su , then after this i could su in command line
but still a lot of problem exists like when i logined before i didn’t have to run knetworkmanager to have my internet up and running but now i have to :((

whats wrong with this kgrubeditor , i checked it in kde-apps but there everyone praised it so what the matter ???