just noticed this recently when I decided to change my wallpaper, luckily I have back ups of these pictures. but when I load an image on the SD card from my PC and then when the phone reloads the card it will delete all the data within the file. I even tried renaming the directory to see if this will resolve the issue but it doesn't the phone still continues to destroy the file. it will destroy images from zedge as well. it does preserve a few files that were loaded by scanner or by the camera. so those are the only ones still viewable. this is a rooted phone fyi not sure if it matters in this case. I discovered the problem with vanilla rom, and then swapped back to eris2.1official. phone still does it.