Frustrating Ferret

I stuck in search element problem. I am trying to install ferret on my
window 7. But tried a lot but couldn’t succeed.

I ran following command to install the ferret gem.

gem install ferret
gem install ferret --version (all versions)
gem install ferret -v 0.11.5
gem install ferret -v 0.11.6
gem install ferret -v 0.11.8.4
gem install ferret -v=0.11.6 --platform mswin32

I also changed the devkit, got a updated kit and change requisite path
in fstub

But couldn’t succeed. Always it gives me following error
ERROR: Error installing ferret:
ERROR: Failed to build gem native extension.

    c:/RailsInstaller/Ruby1.9.2/bin/ruby.exe extconf.rb

creating Makefile

make
c:/RailsInstaller/Ruby1.9.2/bin/ruby -e “puts ‘EXPORTS’,
‘Init_ferret_ext’” > f
erret_ext-i386-mingw32.def
.
.
.
.
.
.
ferret.c:297:22: error: ‘struct RString’ has no member named ‘len’
make: *** [ferret.o] Error 1

Gem files will remain installed in
c:/RailsInstaller/Ruby1.9.2/lib/ruby/gems/1.9
.1/gems/ferret-0.11.6 for inspection.
Results logged to
c:/RailsInstaller/Ruby1.9.2/lib/ruby/gems/1.9.1/gems/ferret-0.
11.6/ext/gem_make.out

Please help me.

Any help or suggestion is appreciable.

Thanks
Amir