Originally Posted by Damurs
...System management is locked by the application with pid 6140(/usr/sbin/package kitd)"...
This will be the applet that checks for security updates. You can kill it, as mentioned above, or you can just wait a few minutes for it to finish its checks. Well, assuming that the checks do finish; if there is a problem with your network connectivity, it may never finish, but then, if you have a problem with your network connectivity, you probably are not going to be able to use the network to install applications, anyway.