Question : IIS host header and DNS

I own a domain, lets call it www.mydomain.com and I also have access to Cpanel's WHM which allows me to do nice things with the domain such as adding A/MX/CNAME and etc records.

Having a few company sites hosted internally on IIS I find myself often using the sub-domains of mydomain.com for redirections to let's say Outlook Web Access (outlook.mydomain.com), SBS Remote Workplace (remote.mydomain.com) among few other sites.

Currently having installed a a search ASPX application on a local server, I gave it a host header of search.mydomain.com which played in nicely for a while, however about after 30 minutes since specifying the host header, the url would present me with The Page Not Found (IE8 or FF3).

Having removed the host header , site went back to normal, yet having few sites on a server it has to be accesed via port other then 80, taking away possibility of being accesed with a "clean" url such as search.mydomain.com without utilizing the host header.

I waited for about an hour, and repeated the steps to add a host header for the site.  Once again it played nicely for about 30 minutes and gave me the page could not be found once those 30+ minutes was up.

What can I do at this point besides giving up on the idea of using the host header for this particular site?

Answer : IIS host header and DNS

If you cannot access the site and it is not getting lohgged in IIS then it is likley not getting to the server. This places the problem with the DNS.

use nslookup on your nameservers to see if there are connections. And use tracert to see if you can connect. Check any proxies for a blockage.