On x86_64, it's kded that's pushing to 99%.
That happened to me too with the i386 version. I dropped back to KDE 3.43 and all is OK.
On my work computer I'm also getting the kded loading the CPU to 100%... on a 32 bit install, not 64 bit (even though it's running on an Athlon64). So on 2 different computers I have CPU load problems. On the home computer, Konqueror loads the CPU to 100% until I exit it and kill all instances of Konqueror. I discovered that if I change the Konqueror settings so that it does NOT keep Konq running in the background that when I exit any Konq I have open, it returns CPU load to zero. On my second computer - the one with kded causing problems - I killed the kded process and CPU load returned to zero. So far, no problems have cropped up from killing the kded process. Strange that on 2 virtually identical installs, I get the same problem, but with different apps. C.