It might be a name-convention issue... If your module/class is called
'ActiveExt' then the corresponding .rb file should be named
active_ext.rb (without the underline, it corresponds to the class
'Activeext' without the capital E)
Try to either rename your model or your files accordingly. Make sure
that you're running the latest version of Rails (I'm using 2.1.1 atm)
which encourages you to use ActiveSupport::Dependencies rather than
just Dependencies btw.
You may also create a new project and try it with a non-brainer-plugin
first, like a class that only has one method throwing a certain
string. You should be able to access that class from within your
controller without adding another 'require' command (the one from
init.rb should be sufficient).
One more thing (sorry for the verbose reply) - if you're adding
functionality to some of Rails' modules and classes like for example
ActiveRecord, you might be out of luck. As far as I understand it,
these are generally not being reloaded although there may still be
some tricks I don't know of.