Alright, so removed and added my credit card, and it's the same thing. I should mention that earlier I managed to download most of the ebooks, but there is still one that won't work. It's so random. The others also wouldn't download, and then they suddenly would. I guess this will work at some point.
I don't seem to be able to sideload books. I tried sideloading about a dozen or so books via Calibre. Initially, my nook only showed 3 or 4 of them. No idea why they didn't all show up. So I tried adding them again, but no good. So then I removed them (successfully), and then added the whole bunch again. After disconnecting my nook, the device searches for new content... and keeps on searching. And searching. And searching. I left it for a solid 20 minutes, and it just kept searching in vain.
The files seem to have successfully been transferred to the nook; I can see them in "my documents" in the nook USB drive, but they aren't showing up in the reader for some reason.
Any suggestions? I'm really starting to think getting an e-reader simply wasn't the hassle. At least my paperbacks don't give me f***ing attitude when I try to read them.