Bug with siteurl and home url, "Update siteurl and home as well" keeps unchecking

I have a wordpress network with buddypress installed. All newest stable versions. WP 3.0.4, BP 1.2.7

The issue I have is that, at seemingly random times, a blog may stop redirecting properly. I check the site options page and notice that the “Update siteurl and home as well” checkbox is unchecked for some strange reason. I can check this box and it fixes. Not sure when or why this is happening, but it continues to happen randomly, though not on all blogs, even though all the blogs are created identically.