Yes, I know about that one. The error message is a little too vague, I know (I'll improve on that in the next version).
What's actually happening is that the server is returning a "400 Bad Request" response. I'm not entirely sure why. But the official NTSC MAX Drive program seems to do it too (although its response is even worse -- it claims to have successfully downloaded the list, when it clearly hasn't).
I suspect the server is having issues. Probably the best bet is to go to the CodeJunkies site and tell them that there's a problem with the codelist server. If enough people tell them, maybe they'll fix it. (It hasn't usually been down for too long before this.)
Edit: if it takes too much longer I could upload an old NTSC codelist I've got lying around, so at least those people who are just starting out or are quite out of date could continue. But it is quite an old one -- version 1495. (I don't update very often.)