htaccess problem

[eluser]Unknown[/eluser]
Hi All,

first of all sorry for my bad english

here my background of this problem :
i have 2 project using codeigniter
1 project created by team a name project : client_site
another one created by team b name project : server_site

the structure directory on prod mechine is
:
---- www
-------- application(folder)
-------- system(folder)
-------- .htaccess
-------- server_site(folder)
--------------- application(folder)
--------------- system(folder)
--------------- .htaccess

the problem start today, suddenly when admin cannot log in to the server site( at 9.00am)
when admin submit the login panel, it said that page not found (404), suddenly can log in again at 12.00pm
and this evening at 17.00pm admin cannot log in again, but not problem for client site, they still can access
add / edit / add item, only happen to server site

i don't understand why, or maybe i got wrong code for the application
but when i check the controller and function it's already there
controller home.php with function login()

my bos said, my htaccess maybe got wrong setting

here my htaccess :
on root site(client_site):
---------------------------------------------------------------------------------------------------------------------------------------------
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond $1 !^(index\.php|images|font|banners|buttons|css|detik|js|robots\.txt|favicon\.ico)
RewriteCond $1 !^(index\.php|application/views/|robots\.txt|install|favicon\.ico|documents)
RewriteRule ^(.*)$ /index.php?/$1 [L]
RewriteCond %{HTTP_HOST} !^www\.(.+)$ [NC]
RewriteRule ^(.*)$ http://www.client_site.net/ [R=301,L]
---------------------------------------------------------------------------------------------------------------------------------------------


on server_site :
---------------------------------------------------------------------------------------------------------------------------------------------
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond $1 !^(index\.php|images|img|css|js|robots\.txt)
RewriteCond $1 !^(index\.php|application/views/|robots\.txt|install|favicon\.ico|documents)
RewriteRule ^(.+)$ index.php?/$1 [L,QSA]
RewriteCond %{HTTP_HOST} !^www\.
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/server_site/$1 [R=301,L]
---------------------------------------------------------------------------------------------------------------------------------------------


some one, can u help me?