user timeout

I am running weblogic 6.1sp6 and Apache 1.3.34 with mod_ssl 2.8.25 and
openssl 0.9.8a. The apache proxies to the weblogic server using a
secure connection and the weblogic apache plugin. This setup had been
working well for a long time, we recently PKI enabled the site (apache
requires users to submit a certificate) and now if users are idle for
15 minutes or so - the site becomes unresponsive, users receive a 404
error page no matter what they request. Users are forced to close their
browsers and login to the site again.

The apache error log shows
[Tue Jan 17 20:59:08 2006] [error] mod_ssl: SSL handshake failed
(server gate:443, client 192.168.0.1) (OpenSSL library error follows)
[Tue Jan 17 20:59:08 2006] [error] OpenSSL: error:140890C7:SSL
routines:SSL3_GET_CLIENT_CERTIFICATE:peer did not return a certificate
[Hint: No CAs known to server for verification?]
[Tue Jan 17 20:59:08 2006] [error] mod_ssl: SSL handshake failed
(server gate:443, client 192.168.0.1) (OpenSSL library error follows)
[Tue Jan 17 20:59:08 2006] [error] OpenSSL: error:140890C7:SSL
routines:SSL3_GET_CLIENT_CERTIFICATE:peer did not return a certificate
[Hint: No CAs known to server for verification?]
[Tue Jan 17 20:59:08 2006] [error] mod_ssl: SSL handshake failed
(server gate:443, client 192.168.0.1) (OpenSSL library error follows)
[Tue Jan 17 20:59:08 2006] [error] OpenSSL: error:140710C7:SSL
routines:REQUEST_CERTIFICATE:peer did not return a certificate [Hint:
No CAs known to server for verification?]

Any ideas as to why apache would suddenly start acting that way?

Thanks,
Ash