и я не знаю относится ли это к вопросу, но при error_log info в лог заносятся пачками сообщения вида

2012/09/18 22:08:32 [info] 40545#0: *3946 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40545#0: *3950 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40545#0: *3951 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40545#0: *3952 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40545#0: *3954 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3956 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3957 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3959 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3961 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3962 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3963 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3965 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3966 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3967 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3968 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3969 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3970 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3972 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80
2012/09/18 22:08:32 [info] 40550#0: *3977 client timed out (110: Connection timed out) while reading client request line, client: 91.212.217.236, server: 0.0.0.0:80

и

2012/09/18 22:08:32 [info] 40559#0: *4497 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru
2012/09/18 22:08:32 [info] 40558#0: *4603 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru
2012/09/18 22:08:32 [info] 40559#0: *4490 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru
2012/09/18 22:08:32 [info] 40559#0: *4494 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru
2012/09/18 22:08:32 [info] 40558#0: *4598 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru
2012/09/18 22:08:32 [info] 40559#0: *4493 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru
2012/09/18 22:08:32 [info] 40559#0: *4491 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru
2012/09/18 22:08:32 [info] 40559#0: *4489 client prematurely closed connection while reading client request line, client: 89.22.22.11, server: coolsite.ru

примечательно что такие сообщения повляются пачками (обратите внимание на время и айпи клиента)