I believe I am having a similar issue. I am very new to Ruby/Rails/Radiant, so please bear with me.
I installed Radiant 1.0.1 on my Dreamhost shared account using 'gem install radiant', then installed radiant to the root of my domain. I configured database.yml to connect to my mysql instance, ran 'rake production db:bootstrap'. I am getting an error from Passenger now: 'You have already activated rack 1.2.1, but your Gemfile requires rack 1.1.3. Consider using bundle exec.' It appears as if radiant-1.0.1 requires rack 1.1.3, but the Dreamhost environment already has 1.2.1 installed. It seems like there must be some way to isolate my environment and run whichever version of rack is required... or should I update the app to allow rack 1.2.1? I'm not sure which solution is preferred, or possible, or how to implement either solution. I appreciate any feedback you can offer! -Chris
