libMagickCore.so.4: cannot open shared object file:

/usr/local/rvm/gems/ruby-1.9.2-p290@global/gems/activesupport-3.1.1/
lib/active_support/dependencies.rb:240:in `require': libMagickCore.so.
4: cannot open shared object file: No such file or directory - /usr/
local/rvm/gems/ruby-1.9.2-p290@global/gems/rmagick-2.13.1/lib/
RMagick2.so (LoadError)

I get this error when I try to start my app. Any ideas?

I checked and this file does exist: /usr/local/rvm/gems/ruby-1.9.2-
p290@global/gems/rmagick-2.13.1/lib/RMagick2.so

I had to do this
ldconfig /opt/lib/imagemagick/lib

I have an arch linux, and had the same problem.
What works on me was install directly the rmagick with the gem
installing (apart from the added on the Gemfile)

    gem install rmagick