I have two users that are having similar problems. RTMPDump seems to connect ok for them, but then they get an Access Denied error. The weird thing is it happens after the authentication handshake succeeds. I thought at first perhaps the authentication token might have become invalid or something, but the error seems to occur almost straight away.
Here's pastebins of the two users debug output:
http://pastebin.com/EshYh9R9
http://pastebin.com/WvMhbxZi
Can you guys see anything in there that might point to the problem?