Thank you for alerting us about this. Can you let us know what browser and version you are using so we can investigate this further? Also, is this happening only for the listing that you mentioned in your question, or have you had this experience with your other listings as well?
Thank you in advance for giving us this additional information. You can post that here or you can send it to our Customer Service team via the link below.
I find Trulia to be very slow and annoying when dragging and moving the photos of my listings. I suggest you try again moving just one photo and waiting until the move is complete (be patient) then try to move the next one.