When an object is marked as non-singleton. I.e. its singleton attribute is set to 'false', or its scope attribute is set to 'prototype' the mothod invocations aren't
being called on the resulting objects.

I've attached a sample application that illustrates the problem.

In the configuration you will see one object:

<object id="tst" class="com.classes.TestObject" singleton="false">
  <method-invocation name="changeTest"/>
</object>

The changeTest method will change the 'test' property to 'true' but as you will by the value on the labels it remains 'false'

if you change the markup to this:
<object id="tst" class="com.classes.TestObject" singleton="true">
  <method-invocation name="changeTest"/>
</object>

the method does get invoked on the right object and thus you will see the labels change accordingly.