If you think the issue is a permissions problem, then as root perform a chown username:username on your user home directory. Or, perform a find ~ -user root and find ~ -group root. Sometimes when working as root people accidentally copy files to their user directory but do not modify the ownership permissions.
If that reveals nothing then one trick that often helps me resolve some KDE issues is to exit X/KDE and then temporarily rename the .kde directory to something like .kde-old. Then start X. You have to tolerate all the default KDE settings, but if KSysGuard then runs okay you at least know that there is a KDE configuration issue with your settings. If the KSysGuard problem persists using the default settings then you know the problem lies elsewhere.
Another trick I have used sporadically is to again exit X/KDE and then delete all user related KDE temp files. There are three directories storing this information:
If you do not want to lose certain files such as favicon files, then rename those directories rather than delete all underlying files. KDE will rebuild the directories and you later can copy files as desired.
Another issue that tends to hit some people are stale or corrupted session files. Those files are stored in ~/.kde/share/config/session. Delete those files outside of X/KDE.
You might want to delete any files found in ~/.kde/share/apps/ksysguard. You also can delete the ~/.kde/share/config/ksysguardrc configuration file.
Lastly, again outside of X/KDE, delete any .DCOP*, .ICEauthority and .Xauthority files in your home directory. KDE and X will rebuild those files.