Hi,
I've just tried your steps (on a 1.2 release candidate, I admit) and it worked fine.
I modified contentModel.xml as follows (additions in bold):
<type name="cm:content">
<title>Content</title>
<parent>cm:cmobject</parent>
<properties>
…
</properties>
<mandatory-aspects>
<aspect>cm:versionable</aspect>
</mandatory-aspects>
</type>
There's one thing you can try - modify the line in core-services-context.xml:
<bean id="importerBootstrap" class="org.alfresco.repo.importer.ImporterBootstrap" init-method="bootstrap" depends-on="alfrescoUserStoreBootstrap">
to:
<bean id="importerBootstrap" class="org.alfresco.repo.importer.ImporterBootstrap" init-method="bootstrap" depends-on="alfrescoUserStoreBootstrap, versionBootstrap">