Comments keep being disabled

After a certain period of time, my comments are disabled and I am unable to enable them. I verified this is a time issue because I changed the post’s date to a more recent one and I was able to enable comments. Can someone tell me how to get rid of this ‘feature’? I rather that readers be able to post comments for any blog entry.
I am using version 2.0.2 of WordPress, and everything is pretty much using the exact default setup.