websites going down for internet clients but still available on the internal lan

Hi,

I currently have a weird error happening on one of my IIS Servers.

The server is currently a Windows Server 2003 server with service pack 2.
The server is running IIS6 and is currently contained inside a VMware
environment. We have multiple IIS servers within this environment however
only this one is experiencing the issue.

The IIS Server has a single network interface card. The card has multiple IP
Addresses each for a different web site which is hosted on this box.
Multiple gateways are setup for access to the internal lan and internet with
different metrics set for each. The internet gateway has a metric of 15 and
the internal network gateway has a metric of 100.

The problem is that the web server will run perfectly for a couple of hours
and then out of the blue will stop responding to hits from the internet.
Browsing to the site merely bring up page cannot be displayed with no
additional information. The page can still be browsed from the internal
network. The only way to bring the page back online for the outside world is
to log on to the console of the 2003 server and open the web page on there.
As soon as that is done the page works perfectly for a couple more hours
until the same happens again.

There are no errors in the event logs and the http logs also look clean. Our
networking team has looked at the firewalls and NAT rules all of which look
perfect to them. We have tried moving the VMware server to another ESX host
which is patched in to different switch ports but still no joy.

Any ideas on possible solutions?

Many thanks
Richard