ну куда понятнее - найти error.log и читать происходящее в момент получения белой страницы
[Sun Oct 14 11:28:54 2012] [error] [client 91.203.147.23] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/administrator/language/ru-RU/ru-RU.plg_system_J2top.ini
[Sun Oct 14 11:28:54 2012] [error] [client 91.203.147.23] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/404.shtml
[Sun Oct 14 11:29:37 2012] [error] [client 91.203.147.23] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/administrator/language/ru-RU/ru-RU.plg_system_J2top.ini
[Sun Oct 14 11:29:37 2012] [error] [client 91.203.147.23] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/404.shtml
[Sun Oct 14 11:29:42 2012] [error] [client 95.69.164.40] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/templates/ukr5/images/MenuItem.png, referer:
http://ukr-on.net/[Sun Oct 14 11:29:42 2012] [error] [client 95.69.164.40] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/404.shtml, referer:
http://ukr-on.net/[Sun Oct 14 11:29:43 2012] [error] [client 95.69.164.40] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/plugins/system/J2top/arrow.gif, referer:
http://ukr-on.net/[Sun Oct 14 11:29:43 2012] [error] [client 95.69.164.40] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/404.shtml, referer:
http://ukr-on.net/[Sun Oct 14 11:29:43 2012] [error] [client 95.69.164.40] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/plugins/system/J2top/arrow_active.gif, referer:
http://ukr-on.net/[Sun Oct 14 11:29:43 2012] [error] [client 95.69.164.40] File does not exist: /home/ukronnet/domains/ukr-on.net/public_html/404.shtml, referer:
http://ukr-on.net/ вот последнии 10 строк что тут не так?