Could you provide more detailed scenario, where you put the breakpoint on which the debugger did not stopped. E.g.
following scenario works for me:

  class Hi

    def hey
      puts 'hey'
    end
    module_function :hey # breakpoint here

  end

Thanks.

Or simple Rakefile or the snipped would be helpful. Debugger does not recognize whether it runs Rails, Rake or simple
script. All is treated the same way.

This is my tarantula test generated for the tarantula plugin from thinkrelevance.com

require "#{File.dirname(__FILE__)}/../test_helper"
require "relevance/tarantula"

class TarantulaTest < ActionController::IntegrationTest
  fixtures :all

  def test_tarantula_admin
    club = Club.find_by_subdomain('myclub')
    p club.name
    post '/signin', :username => 'testadmin', :password => 'nimdatset'
#    assert_response :redirect
#    assert_redirected_to '/'
    follow_redirect!
    t=tarantula_crawl(self)
#    t.handlers << Relevance::Tarantula::TidyHandler.new
    t.crawl '/'
  end

  def test_tarantula_user
    club = Club.find_by_subdomain('myclub')
    p club.name
    post '/signin', :username => 'testuser', :password => 'resutset'
    assert_response :redirect
    assert_redirected_to '/'
    follow_redirect!
    t=tarantula_crawl(self)
    t.handlers << Relevance::Tarantula::TidyHandler.new
    t.crawl '/'
  end
end


In this specific case, 

"fixtures :all" 

launches a process to load the fixtures into the test database; however, I am unable to break on this line, or anywhere
within the processes this line invokes.  The first line I am able to debug/break on is 

"club = Club.find_by_subdomain('myclub')"

within test_tarantula_admin

I see. First what comes to my mind is that the Test Runner 'steals' the interpretation from the debugger and debugger
does not get it into the game until the tests are loaded. Just a guess (CCing Erno).

Debugging Rake::TestTask does not work since the task forks execution with Kernel#system call (see Rake::TestTask#define
method in Rake source). Will try to find how can be workarounded in NetBeans or whether the patch to Rake is needed.

Strange is that you said that you can hit breakpoint inside your test methods. How do you actually trigger the test
case, you wrote:

> When debugging a rake task (and possibly other tasks), if the class has
> precursor operations like "fixture :all" 

The TarantulaTest had to be loaded by some task. Are you using standard:

  require 'rake/testtask'

If yes, you should not be able to stop on any breakpoint when running through Rake Runner -> test task. Or do you have
your own?

I used the Debug Rake Task menu option and selected to debug the Tarantula test task.

Since Tarantula is designed to run the TarantulaTest I included above, I put breakpoints in the class methods and
launched the task for debug.  The key is I needed to start with the fixtures :all and step into the underlying calls for
that task to debug a fixture loading issue.

Unfortunately, the breakpoint on fixtures :all was skipped.

The system did, however, stop on the breakpoint I placed on the first line of the first test method.

*** Bug 182344 has been marked as a duplicate of this bug. ***

This will have to wait still, likely needs changes in the test task itself to be able to hook the debugger when the execution is forked.