Tried to change subdomain name…and failed. HELP!

Okay, I think I made a BIG mistake here. I’ve recently set up a blog at http://blog.sympathytea.com, but I wanted to change the subdomain name to “art” instead of “blog”. I couldn’t find anything about changing it on the forums or on Google, so I tried to do it myself. Basically, I first went under “Edit” on the Dashboard and change the blog URL to what I wanted. Then, I went in and renamed the subdomain and its folder in my server. On the website host, Lonex, it says it takes up to 10 minutes for a changed domain to show up on the server, but it’s been over two hours and when I try to go to http://art.sympathytea.com, the browser doesn’t recognize it at all. The biggest problem with all this is that I can’t access the Dashboard through either website, and so I can’t change it back to the way it originally was.

Please help!!