FWIW, I'm seeing this now - having moved from a Mageia 1 to Mageia 3 system (same hardware)
AMD Phenom II x6
ATI Radeon 4290 (using default 'radeon' driver)
12GB memory
1TB disk
System is still functional (as I have a putty session from an XP system), and I can kill startkde, get the kdm back, and run again successfully for 3 more days. After the second killing startkde, I wind up having to reboot.
I thought it was the driver, but before I went to install the radeon kernel, I tried Xfce and now no lockups for > 3 days. I like the KDE calendar tool (KOrganizer), so I'm running it - but it requires Akonadi

Having read through this set of entries, I'm wondering if I should kill akonadi and search for a different calendar tool - or if it's an interaction between KDE and Akonadi.
jerry