This is a complete rewrite of my original post in light of today's developments.
Yesterday I updated two packages (one being gclib as I recall). More updates appeared, but also a message to reboot, which I did first. After that I have been unable to log into my KDE desktop. The DM appears and after entering my ID and password, the system works for a while then loops back to the DM login screen. I tried booting in recovery mode with the current kernel and a couple of old ones, but each hung up at a slightly different point.
Today I successfully logged into IceWM and completed the update process. I am currently working in IceWM as I am still unable to log into KDE.
I have Mageia 5 KDE running on an Asus laptop with an i5 CPU and an nVidia graphics card which I dual boot with Win7. A month or two ago I changed from Grub to Grub2 as a bootloader with no problems after that. Everything seems to work well in IceWM (including the installed KDE applications). Any ideas would be appreciated.