Left Sidebar widgets only showing up on home page

A few months back, I added a left sidebar to my site, which uses a heavily-customized version of the Twenty Ten theme.

Despite my best efforts, I was never able to make widgets within this new sidebar behave quite the way I wanted them to. I’ve just kind of dealt with it for a while, but I’m feeling motivated today, so I would love to get this fixed.

At the moment, I’ve got three widgets set up in the left sidebar. The picture, the text immediately below it and the mailing list sign-up box. These all show up fine on the home page. But on the other pages on the site, the mailing list widget disappears. This also happens with any other widget I attempt to add. The top two, though, remain normal.

Any idea why this might be?

Any help would be greatly appreciated…