pen hangs on Solaris10/SunFire_T1000

Hello!

I tried using pen on a high loaded web server, distributing requests to
dedicated FastCGI servers via mod_fastcgi's FastCGIExternalServer.
I mean: (inet) <-> apache <-> mod_fastcgi <-> pen <-> multiple wrappers

Pen worked fine for a while, but sometimes it utilized 100% CPU and
stopped answering to requests and USR1 signal.

How can i fix/debug it?

OS: Solaris 10
Hardware: Sun Fire T1000

There is plently of free mem and system load is about 0.5 (normally)

/opt/csw/bin/pen -c 1 -S 2 -x 500 -r \
-p /var/run/pen.pid -w /opt/csw/apache2/share/htdocs/pen.html \
127.0.0.1:9000 192.168.20.35:9000 192.168.20.33:9000

Apache server-status:
CPU Usage: u360.46 s643.49 cu0 cs0 - 1.47% CPU load
114 requests/sec - 0.6 MB/second - 5.3 kB/request
724 requests currently being processed, 83 idle workers

-- 
Best regards,
 Vadim Pisarev