There was a bug in learn mode this morning that was causing it to fail terrifically . Sorry, it was completely my fault.
Not that it matters to anyone, but the problem was one character in my 30,000 lines of code. I found the right character to fix though :)
It's fixed now. Thank you to the 17 people who reported it. Sorry again! -Andrew
Update: it appears I had it programmed right on my local copy, but there was a bug in the code that synced the files from local copies of Quizlet to Quizlet.com. So um, I just reuploaded EVERYTHING in case the problem happened to more than just the Learn page. If you're still having problems, you can email me at andrew at the domain that this website is, or AIM me (sn: Harc Serf).