Subsite won't honor theme selected, always uses system default

Hi, I'm not sure if this is actually a bug report or a support request. I've set up a subsite and set it to use another theme (Garland in this case), instead of the system default. I'm finding that it won't honor this theme no matter what I've tried - it always uses the theme set as the system default. It will however, honor css overrides under Look and Feel, as well as block visibility for the subsite, so I know that it is working. I've tried clearing the cache as well, and tried it with several of the out-of-the-box themes, including trying an out-of-the-box theme set as the default. I'm currently testing this on my local version on my laptop, with Subsites 6.x-1.4, Drupal 6.19, and I'm running on XAMPP. Any ideas?

Thanks!
Alexia