Can't get PDFWRITER to work with RoR

I have a rails app in which I have froze the rails gems and unpacked the pdf-writer gem as all as it’s dependencies into the Vendors directory. I chmodded the dir recursivelty to 755 for good measure. But when I try to run dispatch.fcgi from the consol I still face this error:

/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:18:in require__': no such file to load -- pdf/writer (MissingSourceFile) from /usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:18:inrequire’
from …/config/…/vendor/rails/activerecord/lib/…/…/activesupport/lib/active_support/dependencies.rb:147:in require' from ./../config/environment.rb:54 from dispatch.fcgi:21:inrequire’
from dispatch.fcgi:21

Any ideas?