Footer scrolling after updating to 4.1.0.0

I just updated to version 4.1.0.0 and now the footer is on top of part of the page and scrolls with the page (covering whatever it was when the page loaded).
Is this a bug or did some setting from 4.0.2.3 cause this?

I hope you didn't do it for a live site. Upgrades almost always cause issues, better to do a fresh install. Also bear in mind there are still a number of bugs, with bugfixes applied to the upcoming 4.1.0.1 release, so better to wait for the latter to be released. Or you can use OC 3.0.4.0 which is still the most stable release for live sites.