After installing Blogs MU, my site is no longer accessible - just a blank white screen

I just attempted to install the Blogs MU theme by following the instructions at

After making the theme available to all of the sites within my installation, I went to the Appearance -> Themes menu and clicked the "Activate" link for the Blogs MU theme, and I got a blank white screen. Now the site is no longer accessible.

I tried changing the directory name of the theme in an attempt to get around whatever the issue is, but that didn't work. I also tried modifying the current_theme field in the wp_options database table to the name of the theme that I was using previously, but I'm still running into the same issue.

I also looked at the PHP memory limit, but that is currently set to 64MB.

Has anybody else seen this before?

Thank you for any help you can offer.