Apparently this is usually happened when two or more users are logged in to the same machine. Instead of log out, the next user just use the Switch User to login.
Seems like it will only work correctly when there is only one user logged in. In my case, I would resort to Administrator profile and log off the others from Task Manager > Users tab > select user and click Logoff.
Once this is done, you may try the Software Center again.
Hasbi Notes 