Issue with plugin settings URL's

I’m trying to help a buddy, but this one has me stumped. The blog is installed in a directory (i.e. example.com/blog). Everything works fine except the links to plugin settings. They all drop the /blog/ out of the URL. I’ve checked the General settings and the WordPress Address and Site Address both properly have /blog/ in them.

As far as I can tell everyting else on the site works fine. It’s simply the links to plugin settings (within the admin interface) that are not working.

Thanks in advance for any suggestions or insight.