Script.aculo.us drag and drop problem

Hello,

I am using Script.aculo.us helpers "drop_receiving_element" and I get
a "calling against a nil object" and a NoMethodError exception. I used
the same code un Rails 1.2.6 and it works:

the drag code is:

Code : - fold - unfold

   1. <div id="dropHelperDIV" class="pink box">drop here.</div>
   2. <%= drop_receiving_element :dropHelperDIV, :hoverclass =>
'hover' %>

and it returns this error

NoMethodError in Chapter4#draggables

Showing chapter4/draggables.html.erb where line #21 raised:

You have a nil object when you didn't expect it!
You might have expected an instance of ActiveRecord::Base.
The error occurred while evaluating nil.[]

Extracted source (around line #21):

Code : - fold - unfold

   1. </div>
   2. <div id="dropContainment" class="pink box">drop here.</div>
   3. <%= drop_receiving_element :dropContainment, :hoverclass =>
"hover",
   4. :containment => "'one'" %>

Can anyone help me solve this error?

Thanks,