plasma desktop eats CPU in F16

I am running Fedora 16 which was created from an F15 install via preupgrade. Note though that the homedir is in a separate filesystem and hasn't been re-created for some time, so there might be cruft in it. The desktop is very slow in refreshes. If I change virtual desk pages then the previous page still shows for some time and the system monitor widget shows CPU is high. Top confirms the CPU hog is plasma_desktop, and strace shows stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2183, ...}) = 0 I saw a note via google to remove $HOME/.kde/share/config/plasma-desktop* and doing that did solve the problem but the problem is back. Deleting those means configuring my desktop again, I'd rather avoid that if I can! Zebee