I've taken note of the log files that support mentioned in email, but a.) I don't know what's fit for public consumption; and b.) I'm not sure where to upload anyway.
Initially, I thought that none of the movies were able to play but I had apparently only been trying my 1080p flicks. The cover art still displays fine, but when I start a 1080p movie playing the screen goes black on the latest generation Apple TV and Roku gives the error message that the media server is unavailable or something to that effect.
I have a very capable Hackintosh for transcoding and have quite speedy internet (~300mbps). In fact, multiple Blu-Ray streams simultaneously have never been a problem...until updating Plex Media Server to 2.5.2 yesterday.
Thank you in advance for the help!