After updating my Rails version to 3.0.7 I have been experiencing the error:
The specified module could not be found. - C:/Ruby192/lib/ruby/gems/1.9.1/gems/mysql-2.8.1-x86-mingw32/lib/1.9/mysql_api.so (LoadError )
This occurs every time I try to load the Webrick server.
The solution is to find the "libmysql.dll" file and copy it to your Ruby bin.
The location of these folders on Windows 7 is:
C:\Program Files\MySQL\MySQL Server 5.5\lib
As soon as that DLL is copied you can start the server without any problems.