There's nothing wrong with your DNS. The domain name is resolving to the right thing. Your web server is generating the 302 redirect, because while the visitor asks for / they are being redirected to the default index page with a 302.
302's aren't a problem unless you're experiencing an actual issue.
Google returns a 302 redirect for example,
wget -S http://www.google.com
--2011-08-16 21:30:39-- http://www.google.com/
Resolving www.google.com... 188.8.131.52, 184.108.40.206, 220.127.116.11, ...
Connecting to www.google.com|18.104.22.168|:80... connected.
HTTP request sent, awaiting response...
HTTP/1.0 302 Found
Content-Type: text/html; charset=UTF-8
Date: Tue, 16 Aug 2011 20:32:01 GMT
X-XSS-Protection: 1; mode=block
In summary - you need to look at IIS.