This is common problem when you're trying to index from the browser and your php script is timing out.
Because it never finish, magento is stucked with "processing" state forever.
That's why it better to run indexer from SSH command line. http://php4u.zendesk.com/entries/20254616-how-to-rebuild-lucene-index-from-command-line-ssh
To change status of the indexer you can do it by running mySQL query:
UPDATE `index_process` SET STATUS = 'pending' WHERE `indexer_code` = 'rebuild_search_index_lucene';
You can remove locks from /var/locks folder as well if you have message that indexer is already running