[solved] 503 error - only in WP backend

[Jesse]

Hey guys,

Hoping someone can lend me a hand here. We've got a website which works fine, except when using the wordpress admin panel - which under LS 4.1.12 provides a 503, but switching back to Apache it works without issue.

The errors logged are:

2012-05-14 10:41:37.042 [INFO] [112.xxx.xxx.xxx:56798-0#APVH_domainname.com.au] connection to [/tmp/lshttpd/APVH_domainname.com.au_Suphp.sock] on request #0, confirmed, 1, associated process: 871422, running: 0, error: Connection reset by peer!
2012-05-14 10:41:37.320 [INFO] [112.xxx.xxx.xxx:56798-0#APVH_domainname.com.au] connection to [/tmp/lshttpd/APVH_domainname.com.au_Suphp.sock] on request #0, confirmed, 1, associated process: 871423, running: 0, error: Connection reset by peer!
2012-05-14 10:41:37.591 [INFO] [112.xxx.xxx.xxx:56798-0#APVH_domainname.com.au] connection to [/tmp/lshttpd/APVH_domainname.com.au_Suphp.sock] on request #0, confirmed, 1, associated process: 872453, running: 0, error: Connection reset by peer!
2012-05-14 10:41:37.591 [NOTICE] [112.xxx.xxx.xxx:56798-0#APVH_domainname.com.au] Max retries has been reached, 503!
2012-05-14 10:41:37.591 [NOTICE] [112.xxx.xxx.xxx:56798-0#APVH_domainname.com.au] oops! 503 Service Unavailable
2012-05-14 10:41:37.591 [NOTICE] [112.xxx.xxx.xxx:56798-0#APVH_domainname.com.au] Content len: 0, Request line: 'GET /wp-admin/ HTTP/1.1'
2012-05-14 10:41:37.591 [INFO] [112.xxx.xxx.xxx:56798-0#APVH_domainname.com.au] Cookie len: 461, wordpress_2036f50e6c89287596add14af138ab02=admin%7C1337128024%7Cef81e4be7fb0272528d49325e46f8d12; wordpress_test_cookie=WP+Cookie+check; wordpress_logged_in_2036f50e6c89287596add14af138ab02=admin%7C1337128024%7Cd2aae93e55ba15e24e3bd4560a4bcada; wp-settings-1=m5%3Do%26m13%3Do%26m9%3Do%26m10%3Do%26m11%3Do%26m15%3Do%26editor%3Dtinymce%26imgsize%3Dfull%26align%3Dnone%26m3%3Do%26m16%3Do%26galfile%3D1%26galcols%3D1%26m1%3Do%26m4%3Do; wp-settings-time-1=1336955225

We've ruled out a custom php set by clearing away their account level custom php.ini, checked permissions, raised their memory_limit to 256M, disabled mod_sec, and have tried without their .htaccess (which is just standard wp mod_rewrite). Just not really sure, and given it's working under apache it's really really strange.

php is 5.3.10.

Any ideas?

Cheers,
Jesse