That warning message is to warn you against the "Urgent limewire update download now" message that shows up in most search results...That file contains a virus and the orange banner is limewire's way of telling you unless you see a padlock on such a file it is dangerous...
The padlock has nothing to do with any of the other files that are downloadable....So happy downloading....
Take a look at this thread it will explain file sizes and viruses on the network...
WARNING: Viruses on network you should be aware of!