BuddyPress.org

Google is your friend:
http://www.google.co.uk/search?rls=en&q=NPH%2BCGI

Although I wouldn’t worry too much about trying to understand this as it’s getting rather technical.

First stop ought to be your web host’s tech support who may well be able to clear up what’s happening quickly and definitively.

Failing a resolution from your web host I would head of to a good tech forum with server sub forums such as SitePoint or DevShed and ask the question there but prepare the question with as much detail of your server set up in advance as it saves people having to ask for the info and will earn you brownie points and a more favorable response.