Having used Morpheus and recently converted to Gnucleus (recommended), I have noticed the same thing. I don't think this is a Gnucleus bug. There are several other reasons for this:

1. People use their download directory as Share directory... This is good if you have lotsa space and doesn't have to delete stuff, but with movies people tend to burn it to CD-R as soon as possible (or so I believe...) So most of your sources may be downloaded files that are now erased. Lesson to learn: Don't share files you're going to burn and delete.

2. The problem about never counting up the retries is more puzzling... I have seen it myself, and believe this may be a bug: The system tries to connect to the different sources, but times out before it is through the list. Then, when the system tries to connect again, it starts from the beginning... Bug? I don't know.

So what can you do, especially about the 90% download that stopped? Just wait! Some day, it will be online again, and you'll get your last 10%.
The main problem about movies is that they are so long that most people sharing them out may do a reboot before it completes. To make it even more complicated, dynamic IPs may confuse the system even more. I usually do a Re-Search on seemingly dead files, but even that only rarely gives results. This is the nature of downloading from a changing network. Sometimes you don't get what you want... Be happy about what you DO get. And btw: Shareaza is also using the gnutella network, so chances of finding your last 10% aren't any better there...