Which save? 1461717?
Each user can only report each save once. I'm not entirely sure why, possibly because the system was only really designed for reporting saves (e.g. for being stolen) rather than comments, and in most cases saves only need reporting once. That error message could probably be clearer too.
Unfortunately, the only person who can change this (either removing the limit, or adding a proper comment reporting system) is Simon, who seems to have disappeared.
If the report button doesn't work, report things by sending a conversation to one of the moderators. Or using IRC or posting in the forum will usually work.