[davidfor]

Originally Posted by Leonatus

Hm, I do not quite understand (once more). After installing a new version of Calibre, it's always necessary to reboot the computer, isn't it? That's what I have done this time also. And "cleaning out the temp directory": you mean simply delete the content?

I rarely need to restart after installing a new version of calibre. If you get prompted to, it usually means calibre was running when you did the install and something couldn't be replaced.

And yes, cleaning the temporary directory can be as simple as deleting everything in it. But, you won't be able to delete anything being used by a running application. Windows does have a way to do this. I think it is part of the disk cleanup tool.

As I said above, the problems occurs to all books (obviously) in the library, might they have resided there for years ore been added recently, edited or not.

The error looks like one people have reported when the path to the temporary directory has a non-standard character in it. In most cases, this is because the character is in the username. The solution is to use a different username, or set the environment variable "CALIBRE_TEMP_DIR" to point to a different directory.