There are dozens of other WP installs on the same server, subject to the same ModSec rules, and none of them has a problem. This is the only WP install that has jetpack installed and it only occurs when JetPack is active. The problem is as follows:
Some actions on the post/page edit screen (so far it seems to be the ones that don't refresh the URL, like UPDATE or configure featured image) show me the following alert: http://i.imgur.com/ULPiX.png
The logs show:
Received From: kvm1->/var/log/httpd/error_log Rule: 1002 fired (level 2) -> "Unknown problem somewhere in the system." Portion of the log(s): body.xml:1: parser error : Document is empty ModSecurity: XML parser error: XML: Failed parsing document. [hostname "www.mydomain.org"] [uri "/wp-admin/admin-ajax.php"] [unique_id "blablah"] ModSecurity: [file "/etc/httpd/modsecurity.d/00_asl_z_antievasion.conf"] [line "36"] [id "330791"] [msg "Failed to parse request body. This may be an impedence mismatch attack, a broken application or a broken connection. This is not a false positive. Check your application or client for errors."] [data "XML parser error: XML: Failed parsing document."] [severity "CRITICAL"] Access denied with code 403 (phase 2). Match of "eq 0" against "REQBODY_ERROR" required. [hostname "www.mydomain.org"] [uri "/wp-admin/admin-ajax.php"] [unique_id "blablah"]
Jetpack is 1.7 WP is 3.4.1 Apache 2.2.15 PHP fCGId 5.3.3
Any ideas? The WP forum has been unresponsive so far. I've sent an email to JetPack support.