The one that gets me is when you do a search, you see the item, and try to download it. Instead of downloading, it kicks over to "Awaiting Sources". Search again and it's still there. But apparently there's no way to get it. Even if you're only seeing a partial, you'd think it would go ahead and start.
As for your problem, you coold be looking at a partial. Or the node could have dropped offline. I take you've tried re-searching and Resuming?
Good luck getting an explanation here for how all this works and what might be going on. I've downloaded the Gnutella development docs. There's got to be an explanation somewhere. Now if I can get time to read them...