I know you'd like to see logs. There are no logs. I know you'd like to see shell, xterm and the like. There is no any particularly interesting shell output.

I know that if I start Konqueror, after a few clicks the system will freeze, and won't respond to any keyboard input (no need to list all the nice compbinations of Alt-SysRq-, Ctrl-Alt-Backspace etc etc etc), nor mouse, nor even my screems: only reset button.

What have I changed? Installed all updates. After that I have system crash everytime I try to run Konqueror.

MDK manual strongly recommends to figure out the reasons for this "worst scenario". Hmmm... Is a clean reinstall the only feasible solution?

Try to run konqueror from command line and see if you get any errors when it pops up, instead of clicking on it. Maybe you'll get something more useful.

What updates did you install?

sure, I was trying to see for any hints in the shell, but the system freezes so I have no chance to see what's up on the shell. Error logs are empty.
Shell is clean as long as konqueror is up, but when it is down, all freezes including shell, mouse, keyboard.

I can tell what updates I installed, there are ca. 40 packages (bugfixes, security, normal updates) recommended by mdk update tool. I installed all of them.