Try deleting your cookies and then logging in again.

Log out and then log back in.

Put the files next to the packed folder, not inside. The game will take care of the rest.

Did you delete the packed folder as well?

Full image of the update screen: http://imgur.com/ArvDpWH

The site was properly fixed so that the upload/update doesn't glitch out with the unknown error, but now it's giving this instead. Am I actually missing something or is it a bug?

I'm trying to update my mod (http://www.moddingofisaac.com/mod/972/paintpalettemod) because I forgot a file in the .rar, but everytime I try to update I get this: http://imgur.com/Wh78lKh
It looks like an error message, and it goes away when I hit enter. Anyone else have this problem/know what's going on?

You have to have screenshot(s) as well.

We're not going to give you Rebirth resources if you don't own Rebirth to begin with.

For the most part, any graphic/music mods you have should still work. Gameplay/.txt mods need to be updated to work with Afterbirth.

I would suggest adding it to you "Favorites" in Windows Explorer if you plan to access it a lot.