This posting is older than 6 months and can contain outdated information.
I can use Remote Buddy 1.18.2 (latest version, default settings, using the included Plex Behaviour), Plex 0.9.3.4 (latest version, default settings), OS X 10.7.2 (latest version) and the Apple Remote without any issues. I'm not using Little Snitch.
Since nobody else has brought any such issue to my attention either, I'm afraid there's nothing for me to fix.
As I mentioned before, Remote Buddy sends UDP packets to control Plex and XBMC. If these UDP packets are blocked, control no longer works.
Since Little Snitch is pretty much the only software I can think of blocking local UDP traffic on OS X - and you have it installed (and you're experiencing this issue) - and I (who doesn't have Little Snitch installed) do not experience the issue, I think it's highly likely that Little Snitch and/or your individual Little Snitch configuration is the cause of your issue.
Since I can't provide support for Little Snitch and also have never used it personally, the only advice I could give you is to back up your LS settings, then completely remove LS - and reboot. Given the info you've provided me with, this should solve your issue. For individual support for LS - including debugging its configuration, please turn to the company making it - Objective Development.
Best regards,
Felix Schwarz
