The first message dialog error is:
Difftool would like to access “~/Library/Application/Scripts/net.langui.SnailSVN.DiffTool
And after clicking on the button 'Authorize', the second message dialog is:
Unable to install difftool.sh to the scripts directory!
message – “difftool.sh” couldn’t be copied because you don’t have permission to access “net.langui.SnailSVN.DiffTool