Rails 3 app breaks Rails 2 app

I've got a VPS with Apache/mod_rails installed. I had a virtual host
set up for redmine (rails 2 app) that was working just fine. Then I
set up a virtual host with my own rails 3 app and got it working, but
now when I try to access redmine, passenger throws up the error: can't
activate activesupport (= 3.0.9, runtime) for ["railties-3.0.9"],
already activated activesupport-2.3.11 for ["rails-2.3.11"]

How do I fix this to get both apps working?