I wanted to try streaming files from my Dropbox account, so I added that service via my iPhone and with iCloud sync it showed up on my AppleTV as expected. Then when I went to check my local library (SMB), the AppleTV gives me wrong user/password. I figured iCloud sync from the phone messed something up, so I deleted the local library on my AppleTV and iPhone. Upon trying to re-add the library, the AppleTV STILL gives me the wrong user/password error, even though I was able to re-add it successfully on my iPhone.
I never watch Infuse on my phone, so having it work there is kind of pointless. I removed all sources through my iPhone and tried to re-add my SMB share through my AppleTV and I STILL get the wrong password–and no, I not typing it incorrectly, I can access the SMB share via my MacBook, iMac and iPhone.