Just a side note, as I've seen this occur over the years and no clue as to why it occurs.
Does this happen to you?
Client calls and says, "I have a customer who can't see the www (or non-www.) version of his web site. A site not found error appears, etc."
Situation:
You have set up personalized nameservers for client (dedicated IP's, etc.), and you cannot replicate the problem from your computer. Both www and non-www work just fine to you, so you chalk it up to nutty client or ISP problem.
Well, it comes up periodically, and the only solution I've found is to dump the personalized nameservers set for client, and set to the default server nameservers.
In case you've seen this before...
I have to wonder whether anyone has reported this, as it's pretty maddening and virtually impossible to troubleshoot as it seems so random.
Anyone, just another cpanel mystery among many...
Best Wishes,
Jim Walker
TVC.Net