Apache :: Awkward Delay / Hang While Using Proxy

I am using apache proxypass to proxy to 4 different ports (java/jsp applications) with the following configurations (for each):

<VirtualHost *:80>
ProxyPreserveHost On
ProxyRequests Off
ServerName *****.org
ProxyPass / http://*****.org:8080/ retry=0
ProxyPassReverse / http://*****.org:8080/
</VirtualHost>

Everything seems work fine until an awkward delay / connection timeout occurs. The web application hangs for about 5 to 15 seconds and starts working normally after that period. It's certainly not the application's issue because everything is fine when using IP address to access it.

When I enabled the debug log in apache, I found out that every time the server seems to hang, the following error appears in the apache error log and the number of apache child processes keep on increasing (ps aux | grep apache).

[Thu Apr 11 10:20:41 2013] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 4 in child 13208 for worker proxy:reverse
[Thu Apr 11 10:20:41 2013] [debug] proxy_util.c(1837): proxy: worker proxy:reverse already initialized
[Thu Apr 11 10:20:41 2013] [debug] proxy_util.c(1934): proxy: initialized single connection worker 4 in child 13208 for (*)
[Thu Apr 11 10:20:41 2013] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 3 in child 13208 for worker http://*****.org:8080/
.....
Also, the access log (access.log) completely stops during that hang period.

This debug message keeps on repeating as long as Apache/web-application is not responding. The application starts to work normally after that duration and the number of apache child process decrease to the normal number.

Apache version : 2.2.16 (Debian)
OS : Debian GNU/Linux 6.0
root@server:~# apache2 -V
Server version: Apache/2.2.16 (Debian)
Server built: Nov 30 2012 08:58:36

[Code]....