WordPress Date Auto Modify Bug

Hi,

Has anyone experienced this weird bug? My old posts are being modified automatically and moved to the front page of my blog. For example, if I have a post dated February 4, 2006, and today is February 4, 2012, that Feb 4 2006 post is automatically changed to Feb 4 2012. Thus, the post will be republished as a latest post.

At first I thought I was hacked, but I changed all my passwords including my hosting account’s password. After 24 hours, my Feb 5, 2006 post was changed to Feb 5, 2012. It was also moved to the front page and re-published as the latest post automatically!

This happened in a few blogs of mine with old posts in the month of February. Some modified posts are dated February 2009, some are 2007. The modified posts are the first few posts of my WP blogs. I disabled all plugins and observed if somebody logs in without my knowledge. After observing it for a few hours, I can conclude that nobody is attempting to login on WP blogs, based on the server logs. All the login attempts are just my IP.

So I assume that this is a weird WordPress bug. A really weird one. If somebody here experienced the same problem as I did, please reply to this thread and tell me how you fixed it. As I tried everything I know to fix it, but to no avail.