If you encounter "Error number 7025-646-* during Urchin log processing, it means that the log file that cannot be read. This may occur even if the log file is group readable. This known issue with "the setuid/setgid functionality of the "urchin" binary. in UNIX-type environments. For security reasons, the Urchin engine will run as the owner of the binary, even if it is started as root. Under this condition, only the exact group-id and not the list of groups will be seen by the application.
To fix this issue you may need to change permissions on the log file to world readable, or change the group to the exact group of the urchin user. This only affects UNIX-type platforms.