> What does the following error msg effectively mean? The 
> error was associated with downloading some .jpg
> Error:  "Unknown (not HTTP/xx) response structure"

Can you provide the URL ? 

This probably means that the server responded using weird 
(non-standard) response - probably a response without any 
headers. Unfortunately some browsers (such as Internet 
Explorer) embedds hacks to accept certain broken responses 
from servers.