Version: (using KDE 4.2.3) Installed from: Ubuntu Packages In the system monitor plasmoids subparts you can configure which elements to show e.g. which network interfaces or which disc partitions. However these settings are not preserved on next login. It always shows _all_ network interfaces and _all_ disc partitions in the system on startup. This affects at least the network and disc space monitor. Don't know about temperature or cpu monitors.
I definitely saw this behavior in KDE 4.2.0 - 4.2.2 but can not confirm it with KDE 4.2.4 Though I checked it only with one of my machines. Another note: network and CPU widgets placed in panel always remembered their settings.
*** This bug has been marked as a duplicate of bug 190523 ***
I just upgraded to 4.2.4 and it seems fixed now indeed.