Drupal 7 theme build

Hi all,

I'm updating a site from 6.23 to 7.22 for the first time in a while. Now that I've run the update, none of the 'out-of-the-box' themes seem to work. All the content is there, but none of the color, graphics, or correct fonts are used. (See attachment.)

I'm pretty sure I've run into this before, but I'm blanking on the resolution. Can someone jog my memory?

TIA!