The problem stems from the SD card. Assuming your DV icons are png's stored on the SD card, when you restart your phone it has to re-scan the SD card for changes. If you move the images files from where they were when you created the icon, DV is referencing a path that no longer exists, so the icons will NO restore, and need to be re-created.
In my experience, if you let the media scanner run (should automatically at start-up), and wait a little while, the custom icon images will restore (as long as you didn't change their location on the SD card).
I wish there was an option to like....double-tap DV icons to change their icons. Would fix this problem as well as let us edit widgets/icons without having to create complete new ones.
Hope this helps!
Avoid changing the location of your images