Access log entries, redacted with #'s (first failed with 400 after a 10 sec delay, second succeeded with 302; redacted information was the same in both cases):

#.#.#.# - - [06/Feb/2011:19:00:50 -0800] "POST /wiki/index.php?title=###&action=submit HTTP/1.1" 400 476 "http://###/wiki/index.php?title=###&action=submit" "Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101206 Ubuntu/10.10 (maverick) Firefox/3.6.13"
#.#.#.# - - [06/Feb/2011:19:01:08 -0800] "POST /wiki/index.php?title=###&action=submit HTTP/1.1" 302 632 "http://###/wiki/index.php?title=###&action=submit" "Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101206 Ubuntu/10.10 (maverick) Firefox/3.6.13"


Corresponding error log entry (redacted, same IP, hostname, and page title as above):

[Sun Feb 06 19:01:03 2011] [error] [client #.#.#.#] request failed: error reading the headers, referer: http://###/wiki/index.php?title=###&action=submit

MediaWiki: 1.15.5-1
PHP: 5.3.3-1ubuntu9.3 (apache2handler)
MySQL: 5.1.49-1ubuntu8.1