I did the right thing and cancelled my participation in the show tonight - but still would love an answer to this issue. Other applications recognize it, such as MidiMapper and Grand VJ Vidmapper - it makes no sense that AE doesn't see it. I can't help but think there is a simple fix to this, if only somebody knows what it is...
After Effects does not come with components for HDMI output.
Your other computer must have had additional components installed that added this functionality.
See this thread for more information:
Thank you, Todd!! That did the trick - I copied all the files in Library/Quicktime folder into my new laptop and presto. I knew it was something crazy easy like that. Thanks again!!