We don't test directly with jFusion, but have had reports of many users getting things working. However, I can't guarantee that combination and across that many sites will work. We do have a tip on our
Common Support Questions
area about how best to configure jFusion. If you haven't already seen it, please check it out. It's the 2nd to last question.
Again, I really don't know jFusion that much, but the config options on that page have been confirmed to work across quite a few different systems.
Hope that helps, but if not, let us know. We'll do what we can, but we may also have to refer you to jFusion's support area which may be able to help understand and diagnose the issue further.. especially since it's working on some of the sites (which should help with debugging the problems with the other sites).
Thanks,
Alex