Can't forward from Apache to Tomcat on second instance

I am trying to create 2 separate environments (dev and test) on one
powerfulUnix server which has 2 network cards, 2 IP addresses, 2 server
names...

Using Apache 2.0.43 and Tomcat 4.1.29/JBoss 3.0.7, mod_jk 2.0.43on Solaris 9, Intranet environment, Cocoon apps.

Everything is fine on the first instance,
but on the second instance when I do http://server2 ,
Apache still can't redirect to second Tomcat/JBoss:

"ForbiddenYou don't have permission to access / on this server.

Additionally, a 403 Forbidden error was encountered while trying to use
an ErrorDocument to handle the request.

Apache/2.0.48 (Unix) mod_jk2/2.0.2 Server at mopppgctxat1.pfizer.com
Port 80"

If I do http://server2:8080 , getting it all right.

I made all internal ports on the second instance different from the
first:e.g. 8080->8180, 8009->8109, etc.
Even tried to change "Listen <ip2>:80" to 81, same error.

Curiously, jk2.properties is totally commented out.
I haven't compiled mod_jk, just copied the binary from the 1stinstance.
Can that be a problem ?

Any help is very appreciated.

Thank you,Oleg.