Edit INI files failed

When I create an Bundle that has to change a ini-file the following error occured.

An error occured while performing the "Edit INI file action". The error message is - "An error occurred while taking backup.".

There was an error that occurred during an action for bundle {Bundle Name}. Would you like to automaticaly verify this bundle and attempt the action agein?

What I see is that ZEN makes a backup of the file with the name of the file with the additional extension .tmp.Backup. But the original is not changed.