Hi Fetimo,
As I said once you upload your Rails 3.1 application on your server, you have to delete “gemfile.lock” then relaunch bundle install. That’s the easiest way to get it works. Well of course for a 3.1 application you have to get rack 1.3.2 or higher so, if you want you can still force this version to be installed by adding this line to your gemfile:
gem ‘rack’, ‘1.3.2’
Ok but that’s not the only error you’ll get if you are on a shared host. And for all the one who want to deploy a Rails 3.1 application on Dreamhost and that are not able to install their own version of ruby and passenger, here’s the temporary fix:
In fact you’ll receive a syntax error. This syntax error is no big deal. In fact, it’s due to the new Ruby 1.9.2 hash syntax. So far you were used to write hashes like this:
{ :key => “value” }
But Ruby 1.9.2 supports a new syntax which is:
{ key: “value” }
And the problem is that Ruby 1.8.7 doesn’t support this syntax, and guess what, the Dreamhost’s Passenger application is based on Ruby 1.8.7. So… If you want to get rid off this syntax error just search for all the new hash syntax (normally they appear in the error thrown by Passenger) and replace them by the old syntax. Ruby 1.9.2 supports both so there’ll be no compatibility errors.
I know it’s a little bit boring, but… I’m sure it’s quicker than trying to install your own version of Ruby and get it works. Believe me I tried on a shared server solution and I had an awful headeach by the end of the day.
Of course, after that, don’t forget to precompile your assets: http://guides.rubyonrails.org/asset_pipeline.html#in-production
And! Yeah in less than a morning, thanks to this solution, I got my Rails 3.1 Application up and running: www.society2be.com (you’ll surely notice that I’m French so… in advance, I beg your pardon for my poor English).
I already asked Dreamhost about Ruby 1.9.2, they told me that they planed to update their Ruby Version but not in the immediate timeframe. They asked me to use RVM locally and gave me this link: http://wiki.dreamhost.com/RVM but… first I already tried with no success, second it’s for VPS or dedicated server and I’m on a shared one so…
I hope It’ll help some people 
Kulgar