My elgg site suddenly shows indefinite redirection error...

Hello,

I am using elgg1.6.1in my site.

Everything was fine but suddenly,the site was unreachable by the browser

In firefox i get this message...

The page isn't redirecting properly


Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

* This problem can sometimes be caused by disabling or refusing to accept cookies.  

I tried to install elgg again.but in the second step,it shows

 

The requested URL /elgg/action/systemsettings/install was not found on this server

My modrewrite works correctly. I don't know where is the httpd.conf file situated in my server... Please Help..