Make sure you indent the blocks inside the list items properly, and that you prepend and follow them with a blank line.
For example, this...
1. This is the first item
2. Enumerators are arabic numbers,
single letters, or roman numerals
block::
pass
print foo
3. List items should be sequentially
numbered, but need not start at 1
(although not all formatters will
honour the first index).
.. image:: http://docutils.sourceforge.net/rst.png
:height: 49 px
:width: 526 px
#. This item is auto-enumerated
...should render like this: