[support] one admin page not working for subdomains

I have the Captcha module installed, and I can configured it on the main domain of my site (http://www.{mysite}.com/admin/user/captcha), but when I log into the corresponding page on one of the subdomains (e.g. http://foo.{mysite}.com/admin/user/captcha), it doesn't display any options. What is going on?? How do I tell behind the scenes (in files or database) what the deal is? (Thanks!) -- --Andrew