I've mounted a reverse proxy in a Debian server that redirects to another server used as load balancer. That server divides the load between 3 apache2 server (version 2.2.3 too).
Sporadically the proxy returns an error and in if I take a look to the logs this says:
[Fri Jan 09 02:34:03 2009] [error] [client 190.18.205.134] proxy: error reading status line from remote server 192.168.36.100, referer: http://www.pinkdingo.com/pd/register/step3
[Fri Jan 09 02:34:03 2009] [error] [client 190.18.205.134] proxy: Error reading from remote server returned by /pd/register/step3, referer: http://www.pinkdingo.com/pd/register/step3

This error don't happens always in the URL reported in the log.

This is the configuration file in the server used as proxy:
ProxyRequests Off
ProxyVia Off     
ProxyDomain .pinkdingo.com
ProxyTimeout 4            

ProxyBlock !pinkdingo.com

        <ProxyMatch "http://192\.168\.36\.100:88/">
                Order deny,allow                   
                Allow from all                     
        </ProxyMatch>                              
        <ProxyMatch http://www\.pinkdingo\.com*>   
                Order deny,allow                   
                Deny from all                      
        </ProxyMatch>