Reported in the comments on my contenteditable plugin:

It crashed with the following message: "Coding error detected, it must be fixed by a programmer: [cachedir]/cachestore_file/default_application/core_pluginlist/con directory can not be created, file with the same name already exists

Reported by 2 users here:
https://moodle.org/plugins/view.php?plugin=editor_contenteditable

Note: this editor does not use any cache - it just seems to be triggered by the plugin installation.

The problem is in the file cachestore - it creates directories based on the first 3 chars of the key - which could be any chars. If this happens to match a reserved name on windows - it gives the described fatal error.