I don't want to embarrass Joe here so I really hope he doesn't mind me posting it.
Long story not-so-short, I setup a live chat so that I could help Joe in real time. We went though every step in order and only that way did the root problem come up, and quite innocently too. I don't think this would have come out in normal forum posting.
Basically I'm putting it down to the user interface of the RailPro Assistant software. The main problem was clicking on the import picture button more than once. This gives the filename in use error, as the picture is already imported into the software.
I'm hazarding a guess that since it doesn't really tell you "successful import" or anything like that after you've done the import picture the first time some will instinctively think it hasn't worked so they try again, which will give them the error.
- Tim