It's not the result of double click on the line in the search result window, it's the result of clicking of the Run Search icon (magnifying glass) or hitting the Enter key while in the entry field to the left of the icon, on the toolbar itself.
If I highlight the word and select "Find occurrences of:" from the context menu then I don't get the error message.
The file is saved, I have "Search Open Files" unchecked in the search options.
I would probably have to zip the whole project and send it to you as the text occurs in multiple files, although at this stage it isn't too big.
Version is SVN 5432
Running Debian Lenny Testing.