This is very odd. At the moment, I have some kind of error in a view, but can't see what it is. Also, no debug output in the web server trace.
The Rails 3.2.2 app is an upgrade from 2.7.10, and I'm using "thin" as my development server. I do get normal debug output when the error occurs in other places.
EDIT: I'm running development, as you can see here:
=> Booting Thin
=> Rails 3.2.2 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
>> Thin web server (v1.3.1 codename Triple Espresso)
>> Maximum connections set to 1024
>> Listening on 0.0.0.0:3000, CTRL+C to stop
EDIT: I can duplicate this behavior by raising an exception in the controller.