using "or" in a search produces bad query

When I try to use the "or" in a search, I get a MySQL error. The query it's producing is below. I don't think the DISTINCT(DISTINCT(..)) bit is legal. Normal and-ed queries work fine.

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DISTINCT(node.nid))) FROM node node LEFT JOIN workflow_node workflow_node ON no'

SELECT count(DISTINCT(DISTINCT(node.nid))) FROM node node LEFT JOIN workflow_node workflow_node ON node.nid = workflow_node.nid LEFT JOIN search_index search_index ON node.nid = search_index.sid LEFT JOIN users users ON node.uid = users.uid LEFT JOIN workflow_states workflow_states ON workflow_node.sid = workflow_states.sid WHERE (node.type IN ('content_kbdoc')) AND (workflow_node.sid IN ('10','3','4','11','12')) AND (node.status = '1') AND ((search_index.word = 'tinymce') OR (search_index.word = 'filter'))