Apache HTTP 2.2.13 - SSL handshake issue

[apauser@xxxxxxxxx]

Dear All,

On my apache 2.2.13, SSL handshake sometimes fails/works.

1) The client connects the server
2) The server prompts the client for authentication
3) The user is prompted to select the its certificate and enter password from its browser.

Using a sniffer, we can see that the request 3) is properly sent over the network but we do not see it in apache.

Investigating the LOG file, we found an error as following for each occurence of the issue:
[debug] ssl_engine_io.c(1958): OpenSSL: I/O error, 11 bytes expected to read on BIO#9ce76b0 [mem: 9d41d28]

- Is the error found in the LOG the reason of the error in SSL handshake?
- What is the reason for such error?

See below my virtual host config:
<VirtualHost _default_:443>

#  General setup for the virtual host
DocumentRoot "/usr/local/apache2/htdocs"
ServerName ausersrv
ServerAdmin ausersrv@xxxxxxxxxxxx
ErrorLog "|/usr/local/apache2/bin/crono
 log
/usr/local/apache2/logs/error-%Y-%m-%d.log"
CustomLog "|/usr/local/apache2/bin/cronolog  /usr/local/apache2/logs/log-%Y%m%d.log" common

SSLEngine on

SSLCipherSuite AES128-SHA:DES-CBC3-SHA

SSLCertificateFile /usr/local/apache2/conf/ausersrv.cer

#   Server Private Key:

SSLCertificateKeyFile /usr/local/apache2/conf/ssl.key/server.key 

SSLCACertificateFile /usr/local/apache2/conf/ca.crt

SSLVerifyClient require

SSLOptions +ExportCertData +StdEnvVars
<Files ~ "\\.(cgi|shtml|phtml|php3?)$">
    SSLOptions +StdEnvVars
</Files>
<Directory "/usr/local/apache2/cgi-bin">
    SSLOptions +StdEnvVars
</Directory>

#SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown
KeepAliveTimeout 15
KeepAlive 5


ProxyPass / http://193.168.125.233/
ProxyPassReverse /
http://193.168.125.233/

</VirtualHost>     

Regards,

Bernard.