From the original post:
Three or four days ago I installed pclinuxos kde desktop without a hitch.
is identical to: the standard KDE
+ additional drivers and software
. Maybe some of the RAID-related tools cause a problem there, or more likely you have a bad burn because there are too many strange behaviors mentioned, which is not normal.
Another suggestion: since the standard KDE installs fine, install it, do a full update, and finally in Synaptic search for and install fullmonty-light
, with more info provided here
, then customize and setup the system to your liking.