I was messing with SP's library forms (I think) a while back. Gave up eventually, because that wasn't really what I wanted. I did manage to break something, somewhere, though. Namely, the links to the default Shared Documents Library point to my
Site Actions > All site content > Document Libraries > Shared Documents links to
The library works fine and is available on its original URL,
/Shared Documents, but the problem is that SP still links it to the custom page, which is not what I intend, and I can't remember what I did to change that.