ARD 3.8 hangs when verifying username and password

OS X 10.10.5 installed on an IMac 14,1 running ARD 3.8

Problem started yesterday.

When ARD launches, it appears to work correctly for maybe a minute. Bonjour and Local Network scanner both pull up the list of machines.

Then, when I try to do anything to one of those machines (like Observe or Control), and I try to authenticate to them, ARD hangs. Moreover, Scanner stops working, and I can't do anything without forcing it to shut off and relaunching it.

Things I've tried:

• Shutting off and restarting (same behavior)
• Uninstalling and reinstalling (same behavior)
• Deleting all settings (https://raymii.org/s/snippets/OS_X-Remove_all_Apple_Remote_Desktop_settings.html) and rebooting (same behavior).
• Using ARD on a different Mac (this worked!)

Note that even though ARD is borked, other services utilizing Bonjour have no problems (like Finder). So, I'd like to repair ARD on this Mac, but I suspect there's an OS level problem affecting it.

Is there a log file I can inspect?