losing session in rails 2.3.2 app using subdomain

hi

i have a 2.2.3 app which i upgraded to 2.3.2
it's a multi-site (using subdomain) that creates one top level session
for all sites.

this is how i change the domain for the session in production.rb:

ActionController::Base.session_options[:domain] = "xxx.com"
# in rails 2.2.2, this is what i used to do:
# ActionController::Base.session_options[:session_domain] = "xxx.com"

strange things started to happen after i upgraded i can no longer
login using restful authentication; it does authenticate me, but as
soon as i'm redirected, it would ask me to login again.

as i said, i use restful_authentication and i also use passenger
2.1.2. anyone can help?
hope i'm not doing smth ultrally stupid...

ps. i posted this question on stackoverflow.com, u can head there to
answer the question if you wish...
http://stackoverflow.com/questions/663893/losing-session-in-rails-2-3-2-app-using-subdomain