I haven't seen this particular query before, but looks like it's related to cron.
If the SQL database is going away, that normally means it's timing out/failing - often due to limits on memory or space. That your host doesn't want to look at it doesn't bode well.
As an "eliminate potential other issues" step, have you optimized/repaired your database recently?
I'd do a database backup, run through these two steps, and see if there's any result.
http://www.siteground.com/tutorials/phpmyadmin/phpmyadmin_optimize_database.htm