Not sure. I'm brand new to xenForo (after many years on phpBB). If it helps the dev's my error is on a nearly clean install of xenForo 2.0 beta 6. The only permission that I have changed is to disallow guests viewing the Forum. Everything else is default setting. I'm not planning on launching the form live for another week or so. So I don't mind trying new installs or anything else that might be of help.
@Chris D I think I narrowed it down, still not sure how/why/ or what exactly is right, but I did a test install on a subdomain to play with it and I was able to duplicate the error, fix it, and break it. Hopefully this pattern helps your troubleshooting. I tested it on my live site and duplicated the a couple working options on there but did not help on the live. Nothing has media on the test site, live has one image each. Only other difference is that the live site has descriptions for the nodes, the test is blank (saved time typing haha)
I thought it might of had something to do with only having three (after all successful trials at 4 nodes. but the last one only has three) The only common theme I see is only 3 nodes with at least one container only. So I was able to fix/break on test site but not fix on live site... yet
Again, hope this helps. I'll keep playing with it.