Hi there,
I see my problem is quite common, unfortunately.
Since I have bought the PRO edition I have met the same problem. If I stop downloading an Avi file before completing it, when I go back and resume it it will always come up with "awaiting/need more sources". I have been trying some file for a week now with the same result.
Apparently, no problem with other files.
I welcome any help. Thanks in advance.