win7,ruby1.9.2p136. gem install rails not working.

Hello! I cannot install rails. `gem install rails` returns:

ERROR: While executing gem ... (TypeError)     incompatible marshal file format (can't be read)         format version 4.8 required; 0.0 given

Interpreter is installed from http://rubyinstaller.org/ . Fresh installation, `gem list --local` returns:

*** LOCAL GEMS ***

minitest (1.6.0) rake (0.8.7) rdoc (2.5.8)

`gem env` returns:

RubyGems Environment:   - RUBYGEMS VERSION: 1.3.7   - RUBY VERSION: 1.9.2 (2010-12-25 patchlevel 136) [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:/Users/user/.gem/ruby/1.9.1   - GEM CONFIGURATION:      - :update_sources => true      - :verbose => true      - :benchmark => false      - :backtrace => false      - :bulk_threshold => 1000      - :sources => ["http://rubygems.org/"\]   - REMOTE SOURCES:      - http://rubygems.org/

Is there any workaround that I can try? Thanks in advance.