http status code 404 - Joomla site "Not found" error -

i have joomla 2.5 site set when try access domain intermittent error on screen saying "not found". happends when visiting www, http:// , http://www.

here error: http://imgur.com/7f6ak

i have done thorough domain , dns , records working expected , resolving correctly around world making me think must joomla error of kind. have tried enter sites domain $live_url in configuration file stil happends.

any or ideas appreciated

in short, it's sometimes not finding site, not knowing if host site or use service...

we experience if haven't copied site across servers on our load balancer - perhaps checking if servers have site, or if host has load balancing , didn't propogated properly. sure apache or htaccess settings same account www or not.