Picasa Question

[oblivion]

I have been using Picasa to view my pictures and I use the program to quickly re-size them. This has never been an issue until tonight when I noticed I had resized two pictures and saved them to my desktop. When I see the thumbnail on my desktop of the pictures in the bottom left corner of the thumbnail is a padlock symbol. I have never seen this before and cannot find anything in relation to it. It lets me open it, email it, edit so not sure why this is there. Any ideas (other than stop using Picasa)