I've got the famous white screen, but only on my home page. Deeper pages load just fine. I moved my
themes directory to
themes-old and made a new
themes directory that only has twentyten in it. I changed my theme to twenty ten. I don't have any plugins enabled, but I moved my plugins directory and created a new, empty plugins directory.
I turned debugging on.
I'm at a total loss here. I did make some theme tweaks today, but I already restored the back up of my theme which didn't help, and anyway I've now set twentyten as my theme.