LoadError - no such file to load

Hello,

I'm trying out RubyMine on Windows XP Pro with Ruby 1.9.2 and Rails 3.0.3 but I'm not able to work with installed gems. For example I installed the gem rdf successfully, I attached it via the Ruby SDK and Gems manager but when I call the rails console and put in "require 'rdf'" I get the message "LoadError: no such file to load -- rdf". When I do the same in the IRB Console I get a "true" after typing "require 'rdf'". I suppose the gem is not really attached to the project. Is there a way to see which gems are actually attached? This happens with all gems that did not pre-exist (for example gem mail causes no problem).

My Gem list is:

*** LOCAL GEMS ***

abstract (1.0.0)
actionmailer (3.0.3)
actionpack (3.0.3)
activemodel (3.0.3)
activerecord (3.0.3)
activeresource (3.0.3)
activesupport (3.0.3)
addressable (2.2.2)
archive-tar-minitar (0.5.2)
arel (2.0.6)
builder (3.0.0, 2.1.2)
bundler (1.0.7)
cgi_multipart_eof_fix (2.5.0)
columnize (0.3.2)
erubis (2.6.6)
ffi (1.0.4)
gem_plugin (0.2.3)
i18n (0.5.0)
linecache19 (0.5.11)
mail (2.2.13, 2.2.12)
mime-types (1.16)
minitest (1.6.0)
mongrel (1.1.5 x86-mingw32)
mysql (2.8.1 x86-mingw32)
mysql2 (0.2.6 x86-mingw32)
nokogiri (1.4.4.1 x86-mingw32)
polyglot (0.3.1)
rack (1.2.1)
rack-mount (0.6.13)
rack-test (0.5.7, 0.5.6)
rails (3.0.3)
railties (3.0.3)
rake (0.8.7)
rdf (0.3.0)
rdf-raptor (0.4.1)
rdf_context (0.5.10)
rdiscount (1.6.5)
rdoc (2.5.8)
rgl (0.4.0)
ruby-debug-base19 (0.11.25.jb2, 0.11.24)
ruby-debug-ide (0.4.15)
ruby-debug-ide19 (0.4.12)
ruby_core_source (0.1.4)
stream (0.5)
test-unit (2.1.2)
thor (0.14.6)
treetop (1.4.9)
tzinfo (0.3.23)

My Gem environment is:

RubyGems Environment:
RUBYGEMS VERSION: 1.3.7
RUBY VERSION: 1.9.2 (2010-08-18 patchlevel 0) [i386-mingw32]
INSTALLATION DIRECTORY: C:/Ruby192/lib/ruby/gems/1.9.1
RUBY EXECUTABLE: C:/Ruby192/bin/ruby.exe
EXECUTABLE DIRECTORY: C:/Ruby192/bin
RUBYGEMS PLATFORMS:
  ruby
  x86-mingw32
GEM PATHS:
   C:/Ruby192/lib/ruby/gems/1.9.1
   C:/Dokumente und Einstellungen/Ich.COMPAD/.gem/ruby/1.9.1
GEM CONFIGURATION:
   :update_sources => true
   :verbose => true
   :benchmark => false
   :backtrace => false
   :bulk_threshold => 1000
REMOTE SOURCES:
   http://rubygems.org/
----------------------
IDE: JetBrains RubyMine 3.0, build #RM-97.125
RubyMine SDK Environment:
Sdk: Ruby SDK 1.9.2-p0
Sdk Version: ver.1.9.2p0 p0
Ruby Interpreter: C:/Ruby192/bin/ruby.exe
RVM Sdk: no
Sdk Language Level: 1.9
Sdk Load Path:
     C:/Ruby192/lib/ruby/site_ruby/1.9.1
     C:/Ruby192/lib/ruby/site_ruby/1.9.1/i386-msvcrt
     C:/Ruby192/lib/ruby/site_ruby
     C:/Ruby192/lib/ruby/vendor_ruby/1.9.1
     C:/Ruby192/lib/ruby/vendor_ruby/1.9.1/i386-msvcrt
     C:/Ruby192/lib/ruby/vendor_ruby
     C:/Ruby192/lib/ruby/1.9.1
     C:/Ruby192/lib/ruby/1.9.1/i386-mingw32
     C:/Programme/JetBrains/RubyMine 3.0/rubystubs19
Sdk Gem paths:
     file://C:/Dokumente und Einstellungen/Ich.COMPAD/.gem/ruby/1.9.1/gems
     file://C:/Ruby192/lib/ruby/gems/1.9.1/gems
     file://C:/Dokumente und Einstellungen/Ich.COMPAD/.gem/ruby/1.9.1/bundler/gems
     file://C:/Ruby192/lib/ruby/gems/1.9.1/bundler/gems

Any help is very much appreciated! Thanks in advance!