WordPress Database Error: Incorrect Key

When I click on the link tag in the visual editor, this error pops up. I have already tried repairing the db via CPanel but it is not working. How can I fix this?

WordPress database error: [Incorrect key file for table './darran_wrdp1/wp_useronline.MYI'; try to repair it]
DELETE FROM wp_useronline WHERE userid = '1' OR (timestamp < 1172840192)

WordPress database error: [Incorrect key file for table './darran_wrdp1/wp_useronline.MYI'; try to repair it]
INSERT INTO wp_useronline VALUES ('1172840492', '1', 'admin', 'darran', 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.2) Gecko/20070219 Firefox/2.0.0.2', '58.182.80.231', 'Lime Touch', '%2Fwp-includes%2Fjs%2Ftinymce%2Fthemes%2Fadvanced%2Flink.htm%3Fver%3D20061113', 'member')

I did not do anything, this error just came up all of a sudden