Descriptive Problem Summary:
Please see the DMCGI error/backtrace at http://files.byondhome.com/Gakumerasara/error_forum.log
This is from version 479, so I guess it's possible this has already been fixed in version 480?
Hopefully the backtrace will be sufficient for you.
This is the one and only occurrence of this error I have ever seen.
I was unable to reproduce the bug by following the same link from the error.