You can remove software centre from the terminal. Then you should clean the
cache or it will just install the old one again. Then re-install software
centre from the terminal. Have you tried Synaptic?
#purge will remove all traces while remove will leave config files
sudo apt-get --purge remove software-center

#clean removes all packages from the cache, but don't do this if you want
to keep the files (debs), such as you are on dial up
sudo apt-get clean

#download (if you used purge) and install a new one
sudo apt-get install software-center

try also

sudo apt-get install synaptic