My site has running for almost a year now.
Since the beginning of this year (2011), I discovered my 3 oldest posts were being automatically updated with the post date on the current day.
I've gone in and edited the date back to the original post date on each of the articles and all was fine.
When I check the next day, the post dates had changed again.
I have no idea where to start checking this problem. I do have quite a few plugins running, but have no idea which one might be (or even is) responsible.
Would be interesting if anyone else is having the same problem and/or a solution.