Index: Solr_Base_Query.php
===================================================================
RCS file: /cvs/drupal/contributions/modules/apachesolr/Solr_Base_Query.php,v
retrieving revision 1.1.4.14
diff -u -r1.1.4.14 Solr_Base_Query.php
--- Solr_Base_Query.php	9 Dec 2008 01:01:29 -0000	1.1.4.14
+++ Solr_Base_Query.php	17 Dec 2008 12:01:07 -0000
@@ -291,7 +291,8 @@
       $subfq = $data['#query']->get_fq();
       if ($subfq) {
         $operator = $data['#fq_operator'];
-        $fq = $this->fq[] = implode(" {$operator} ", $subfq);
+        $subfq_string = implode(' ', $subfq);
+        $fq[] = "{$operator} ({$subfq_string})";
       }
     }
     return $fq;
@@ -302,7 +303,9 @@
     foreach ($this->subqueries as $id => $data) {
       $operator = $data['#q_operator'];
       $subquery = $data['#query']->get_query_basic();
-      $query .= " {$operator} ({$subquery})";
+      if ($subquery != '') { // search keys can be empty, skip it
+        $query .= " {$operator} ({$subquery})";
+      }
     }
     return $query;
   }