Couldn't find MIME type application/octet-stream (Konquerer/Kdesktop)

This is copied from http://users.pandora.be/Ice9/Linux stuff/Linux_tips.html. I have used the second method as the desktop file appeared to be disfunctional judging from its content and had been created during the time when the error appeared first (that was when I was playing with the File associations section of the control center). KDE returns "Couldn't find MIME type application/octet-stream" at startup and/or Konqueror returns the same error message when launching whatever application.
Start the Control Center and open KDE Components/File Associations.
Expand "application", and you will probably see that there's no entry for "octet-stream".
Click on "Add...", for "Group" select "application" and for "Type Name" fill in "octet-stream". This should fix it.

Alternatively, I also read that you could delete the file /home/userID/.kde/share/mimelnk/application/octet-stream.desktop
I tried it and it also works but I'm not too comfortable deleting files without really knowing what they do, so if you decide to do this it will be at your own risk.