It looks like a MySQL query is getting truncated to "SELEC" instead of something like "SELECT * FROM table..." Since this is in the right sidebar could it be a custom plugin? What other mods have you made?
If you have a widget module that displays stuff on the sidebar, try disabling that.
By the way if you want to check whether it's the theme, you may have to go into the database and edit manually if you can't open the admin area. In the qa_options table, find the row with the key of site_theme, and change the content to "Default".