Troubleshooting Passenger issue with Rails app

Here's the subdomain that I'm running a Rails app on:

http://stage.donatella.com.au/

Note the Passenger error message - any clues on how to troubleshoot this?

Illformed requirement [#<gem::requirement:0xb61346b8 @requirements="[[&quot;~">", #<gem::version "1.1.5"="">]], @version=nil>]</gem::version></gem::requirement:0xb61346b8>