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/ (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.