I am trying to configure Solr 4 to work with UUID and so far I am unsuccessful
From reading the documentation I have seen two different ways to configure schema.xml
You may want to remove the Query Elevation component if not using it.
QueryElevationComponent requires unique key to be defined and it should be a string unique key with JIRA.
However, it was fixed with the Solr 4.0 alpha so it would depend what Solr version you are using.
This limitation is documented in the Solr wiki.