Cannot change default style

I have two forums, one "live" using PHP 4.3.11 and MYSQL 5.0., the other "test" on my local maching running PHP 5.2.4 and MYSQL 5.0.? . On the live forum, it was updated from RC3>RC4>RC5>RC6>RC7 and I have not been able to change the default style since RC7. On my "test", it was a fresh install of RC7. I managed to change the default style once, but could not change it again. Even after purging cache & manually deleting the cache. When I look in the database at phpbb_config, it shows the style id # of the one I want as default, but the forum seems to be ignoring it.