The other time I've noticed this error message tends to show up is when you're trying to access BL through an old link (one with 'vb' in the address instead of 'xf').
Normally the site will usually automatically redirect you to the updated link, but when it fails, this "oops" thing is the error message that shows. Again, a refresh will usually resolve this, or else you can click on any other tab on the screen and navigate to where you want to go manually.