Deploying with a proxy kills authorization

[superflyc]

I've deployed Pebble on Tomcat/Apache without any issues, given the following settings:

app-context is pebble
url to access it
http://actual_machine_ip/pebble

and via ajp

http://different_ip/pebble

but when I have an external proxy like this:

http://foo/

authentication breaks. It looks like this is all based off the context of the application. I've changed the URL value in pebble.properties, but this still kept using the context of the application. Is there a setting somewhere that I'm missing?

I've subclassed some of the Acegi code and now my redirects after logging in are going to the right place, but I can't access any protected content and functionality.

thanks!
Chris