All pictures have disappeared from the gallery.  This is second time has happened.  First time just entered card had in my camera and forgot the older pictures.   Today, happened again.  I have also downloaded a photo site, Picasa, which I really like.  All pictures are gone from this site.   How do I recover them and what is happening to cause them to disappear?  Message I get is "cannot locate photos.  I was working on the pictures to transfer to disc to save.      Thank you.

Original title: Photo Gallery