This issue has been ongoing for me for quite some time. Through multiple versions of WordPress. In the General Options tab of wp-admin, the WordPress address section keeps going back to something I had originally set the blog at.
This of course changes all of the links on the website including the style sheets, which makes it extremely annoying to get back to the options tab to update it again.
I'm not sure exactly how long it lasts, but perhaps a few days to a week before it resets. any help?