SolrSearch Problem

Hi. I have installed SolrSearch as a plug-in and also have Apache Solr installed. However, I am getting this error when running a search in Omeka:

Omeka has encountered an error

Apache_Solr_HttpTransportException
'400' Status: Bad Request

#0 /var/www/html/omeka/plugins/SolrSearch/lib/solr-php-client/Service.php(1176): Apache_Solr_Service->_sendRawGet('http://localhos...')
#1 /var/www/html/omeka/plugins/SolrSearch/controllers/ResultsController.php(83): Apache_Solr_Service->search('red', 0, '10', Array)
#2 /var/www/html/omeka/plugins/SolrSearch/controllers/ResultsController.php(48): SolrSearch_ResultsController->_search(0, '10')
#3 /var/www/html/omeka/application/libraries/Zend/Controller/Action.php(516): SolrSearch_ResultsController->indexAction()
#4 /var/www/html/omeka/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('indexAction')
#5 /var/www/html/omeka/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#6 /var/www/html/omeka/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(101): Zend_Controller_Front->dispatch()
#7 /var/www/html/omeka/application/libraries/Zend/Application.php(366): Zend_Application_Bootstrap_Bootstrap->run()
#8 /var/www/html/omeka/application/libraries/Omeka/Application.php(79): Zend_Application->run()
#9 /var/www/html/omeka/index.php(23): Omeka_Application->run()
#10 {main}

Any ideas on how to resolve this?