I will try to replicate the issue on my dev site and see if I can figure out why it isn't getting the files properly. Ideally, I will see if I can check if the image is already on your site, and not duplicate it, as it is currently trying to do.
EDIT: Actually, I just noticed that it works for some and not for others, which is weird. I'll still look at making it not save the image if it already is on your site, but in the mean time, can you delete all of the files in the /dbtech/vbslider/images/externalimages folder and see if that changes anything?