I wouldn't call it common. I've seen it maybe once or twice in the past 5 years, due to powerloss or a hard system shutdown. ..
It sounds like something isn't finished writing data to the hard drive before the system shuts down. the system is failing to sync
before it's powered off.
Superblockl, flag and journal in this instance are all part of your file system.
Since this only occurs when you are running KDE then I would guess that is where the issue lies, the question is why and how do you fix it ?
For testing you could install KDE4 Configure it so it does NOT start automatically at boot.
Boot the system, log in, manually Start X and use it.
When you are done working shut down X, manually sync the filesystem using the sync command linked above. then shutdown.
I would bet using that process, the corruption will not show up again.
The problem is, that should all happen automatically, in the background, without you being aware of the process