Apache mod_ssl give SSL Library Error: 336151570

Hello,
I have very typical problem:
I have a certificate installed for my domain from Thawte. Now if anyone
tries to access the webpage using a browser it works perfect.
Now one of our clients has a proxy server. When they access to our
website using their proxy they cannot access it. They get 500 Internal
Server Error. Our logs indicates the following error:

[debug] ssl_engine_kernel.c(1762): OpenSSL: Read: SSLv3 read client
certificate A
[debug] ssl_engine_kernel.c(1781): OpenSSL: Exit: failed in SSLv3 read
client certificate A
SSL library error 1 in handshake (server abc.com:443)
SSL Library Error: 336151570 error:14094412:SSL
routines:SSL3_READ_BYTES:sslv3 alert bad certificate Subject CN in
certificate not server name or identical to CA!?
Connection closed to child 1 with abortive shutdown (server
abc.com:443)

Now according to them they are doing everything perfect as they can
access another of our SSL server perfectly well. What am I missing - I
am sure our SSL certificate is valid because if I anyone goes through
the browser it works perfectly well.
I am not using client certificate authentication as I have
SSLVerfiyClient none.

Any help is appreciated.

Thanks
Deval