How To Switch Back From New Jira?

So... I was having one problem and then got myself into another problem :)

My "detail view" of Kanban cards wasn't popping up. I took a look at the board settings, tried some different browsers, obvious stuff. So I thought maybe it has something to do with how I had switched to "the new JIRA" a few weeks back and then switched back to normal. So I thought I'd try the new JIRA again and see if the detail view works.

However, my "new JIRA" is broken. All I have is a white screen where I should have my colored borders and menus. If I load my base address, it loads my dashboard in the frame where it should be, but the menus are missing. If I load the address for a kanban board, I get that kanban board (and details view still doesn't work), but still no menus.

So I can't switch back. And I've tried different browsers -- the preference for "new JIRA" is now built in to my login.