cable modem requires reboot because one site falls off DNS?

[Greg Rundlett (freephile)]

I have a strange problem where one (and only one as far as we know)
particular website becomes inaccessible to our office.

The "fix" for this problem is to reboot the Comcast cable modem, however I
don't understand how the modem could be the culprit.

The website in question is nnerenmls.com  and the modem is configured to use
Comcast's DNS servers....
68.87.71.226
68.87.73.242

One red herring:  It would seem that Comcast changed their DNS servers,
because the ones currenty in the modem configuration do not appear in the
list http://dns.comcast.net/dns-ip-addresses.php  I thought to myself, "I
just switch to Google's Public DNS servers" (8.8.8.8 and 8.8.4.4)  I'm
pretty sure they are not going to change.  However, it doesn't make sense to
me that one website would fail, while general DNS would still be working.
 And, at the time of the failures, other people using Comcast can resolve
that domain meaning it doesn't even appear to be an issue where the target
domain is occasionally falling off the web.

Any ideas on what could cause this and how to troubleshoot?

Greg Rundlett
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