Topic: can't install or uninstall ferret

when i try to install ferret i get the following error

Building native extensions.  This could take a while...
ERROR:  While executing gem ... (Gem::Installer::ExtensionBuildError)
    ERROR: Failed to build gem native extension.

ruby extconf.rb install ferret
can't find header files for ruby.
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Then I try to uninstall and i get the following error:

ERROR:  While executing gem ... (Gem::InstallError)
    Unknown gem ferret-> 0

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So now when I rake db:migrate
I get the following error

rake aborted!
no such file to load -- ferret_ext
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I am lost at what I can do.  I can't just not worry about this because I can't rake my Database.  and I can't uninstall ferret. 

This is killing me
Thanks for any help
Dave