I am get this error using mod_proxy

Configuration

 ProxyPass /foo http://www.apache.org/
 ProxyPassReverse /foo http://www.apache.org/

I see this in errorlogs

[Sun Sep 10 02:04:23 2006] [error] proxy: ap_get_scoreboard_lb(0) failed in child 27085 for worker 

....


I have apache 2.2.3

And I have loaded mod_proxy, mod_proxy_http and mod_proxy_balance

any idea?