It's just like the title says. I added 3.53 as a theme, switched to it, imported the settings from 3.49, and made a few minor changes (new menus), but when I'm logged in, the page seems to be visible, but when I log out, all there is is a white screen.

Weird.
I'm back on 3.49 right now, of course.
Any thoughts?

threeguysonebook.com, wordpress 3.01

did you see/read the info under 'export/import settings'?

in other words did you delete the bfa_ata4 as explained there

Yes, I did.

You don't need to import the settings, just switch to 353. Is there anything on the white screen? Did you look at the source p of the page to see if there is anything in the HTML?

I just went back in and switched back to 3.53 and so far it seems to be acting as it should. Fingers crossed.