My Webserver:Windows Server 2003+SQL Server 2000+ASP

Now there is a strange problem:
1.I can ping Domain naem and get the correct IP address.
2.I can access the home page with  Domain name, but  cannot open other
pages such as list page and detail page.
3. ****Most strange thing is I can open all pages WITH IP ADDRESS.
4.After restart machine,all is ok.
5.Some days later,same things appear again.

Tks.

PS:The Server is www.chinaflowerexpo.com, it's a unicode site.