2011 theme sidebar vanishes

I made a modified 2011 theme for a site I maintain, working in Xampp for Windows. Everything was looking good. When I installed the theme on the site, there was no sidebar. On that site, the unaltered 2011 theme does the same thing. Doesn’t matter how much I fiddle with configuration, it goes one-column, and no other menu. Useless.

I can’t figure out what is causing this. I would be grateful if anyone could give me a clue.
PHP Version of site is 5.2.17, home server’s is 5.3.1. Other differences…I can’t say; a lot of variables. But I’ve never had problems with it before. Only the 2010/2011 themes go wonky.

I had just updated the site, and I did an extra manual upload of WP3.2 just to make sure it wasn’t a corrupted file or something.

It’s awfully irksome to have hours of work blow up in my face. 🙁 I think I may have to either work over an older theme or use Artisteer and tweak the graphics.