The error seems to be:
[07/11/2011 8:21 PM] – Advisory : No DL file path conversion performed on URL.
[07/11/2011 8:21 PM] – Status : Dispatching DL method = 1
[07/11/2011 8:21 PM] – FAILURE : Error on fopen (then it lists the URL which is the actual URL of where the image is stored)
Luckily I had ticked that option when setting up initially so have got some history logs there – so the difference seems to be from when it was working and when it stoppped was where the images are stored – would that be likely?
Initially the images were stored in next-gen gallery, so a subdirectory of the wp-content directory. I had put these ones (via ftp) under the main directory (not linked at all to any wordpress directories.
I have just created a subdirectory in wp-content and have tested in the admin setting the link and it is generating a link which prompts for download
Would that have been the solution you would have expected?