I am on Linux Mint 13 64-bit.
KInfo Centre:-
OS Version: Linux 3.11.6-031106-generic
KDE SC Version: 4.11.3

My Dolphin File Manager has started to behave differently and I can't find the cause of it.

I have various LibreOffice documents and Kate notes saved to USB drives. When inserting the USB drive a pop-up window "Available Devices" appears and I always used to open the volume with (Dolphin) File Mananager.

Now, out of the blue, I get an error note: "Sorry-Kate - The file 'file:///media/kanjana/BACKUP2' could not be opened: it is not a normal file, it is a folder."

But I can access the docs in the flash-drive using the Dolphin File Manager icon located in the task-bar.

I tried configuring Kate and Dolphin to various other setting but without luck

I am not a techie... Would appreciate some help here; TIA.

Please open System Settings > Default Applications, and ensure "Dolphin" is selected under File Manager.

Many thanks for prompt response
You hit the nail right on his head! For some reason the default application had changed to Kate which I changed back to Dolphin.
KDE is such a nice looking desktop environment!
Thanks again, I am very happy again

The answer posted here has solved my problem also.

I am curious as to how and why 'Kate' and 'Audacious' would ever appear in a list of defaults -- to be used as a File Manager?

I am tempted to 'clean up' by deleting them as impossible choices, but can anyone think of a reason why they might ever be needed, as 'alternative options' for the *.srt file extension?

Possible clue: in the recent past, I set a .srt (SubRip subtitle) file to open in Kate. I wonder, in KDE, why should opening this, a text file, change the default setting for the File Manager to open a pen drive? It seems I have .srt as a 'filename pattern' for filetype Inode/directory in System Settings -> File Extensions.

Does this suggest anything? Perhaps a defective installation of subtitle composer put that extension where it doesn't belong?