windows installed after the mysql gem error, error is approximately:
ArgumentError (NULL pointer given):
(eval): 3: in `each_hash '
(eval): 3: in `all_hashes'





This is feeling under the windows of the question if the mysql gem version libmysql.dll wrong words (or mysql installation directory has spaces?)
This would be a mistake

Yes my windows vista, mysql 5.1.30, direct copy mysql / bin / libmysql.dll to ruby / bin no longer find the following approach, where to find libmysql.dll from instantrails on ruby / bin inside the effective

Found an effective way to: http://www.ruby-forum.com/topic/172179

If you are having problems with MySQL, getting errors like: The
bundled mysql.rb driver has been removed from Rails 2.2. Please
install the mysql gem and try again: gem install mysql. C: / ruby / lib /
ruby/gems/1.8/gems/mysql-2.7.3-x86-mswin32/ext/mysql.so

Here is the solution: 1) First, gem install mysql. If this doesnt
help continue 2) Copy libmysql.dll from InstantRails (see below) to
your mysql directory (C: \ mysql \ bin \). Restart your computer and it
should be working.

InstantRails libmysql.dll:
http://instantrails.rubyforge.org/svn/trunk/InstantRails-win/InstantRails/mysql/bin/