Apache reverse proxy with client authentication

Hi,

I've searched the internet about apache reverse proxies with ssl, but
there is not much information. It would be nice if someone here can
help me.

What I'm trying to do is to configure an apache reverse proxy with
client authentication against the backend server.

Client ---SSL--- ReverseProxy ---SSL+ClientAuth--- Server

This is, because there is a plugin on the reverse proxy which does the
authentication of the user and I need therefore a secure connection to
the backend-server because I will noch check the user authentication
again.

I use apache 1.3.27 and mod_ssl 2.8.14. The client and server
certificates are in place and the configuration file contains

SSLCertificateFile proxy.crt
SSLCertificateKeyFile proxy.key
SSLProxyMachineCertificateFile proxy_to_server.cert
SSLProxyCACertificateFile server.cert

But if I try to connect with my browser, I get the following error:

SSL proxy connect failed (wfdev.ldn.swissbank.com:8480): peer
160.59.167.149:4443: sslv3 alert certificate unknown


Does someone know what's wrong?

thx
Michael