In modjk (latest version i could find ) for IIS there is a possible bug in 
function:

static int JK_METHOD start_response(jk_ws_service_t *s,
                                    int status,
                                    const char *reason,
                                    const char *const *header_names,
                                    const char *const *header_values,
                                    unsigned int num_of_headers)
{

It creates a response buffer and it works fine if there are headers to send:

            if (num_of_headers) {
                             ...
            else {
however if there are no headers to send it merely sends a single crlf in the 
header buffer. 
                headers_str = crlf;
            }
}

The description for HSE_REQ_SEND_RESPONSE_HEADER at:
http://msdn.microsoft.com/library/default.asp?url=/library/en-
us/iissdk/html/ad17aeb4-bb70-4755-83a2-c4cec7fa5ecb.asp

"If you append your own headers to the server-generated headers, you must 
terminate the header string with an extra carriage return and linefeed."

also seems to mean that once you have no headers to send then you need to make 
sure you terminate the header by adding an extra crlf (double crlf) as per the 
RFC

So sending a single crlf would not be valid (browsers will ignore error this 
but we ran into an app called documentum that crashes while parsing the header.)

Oddly enough IIS copes with and seems to correct the header (at least in Win2K3 
SP1) except in one case and that is where another ISAPI filter is chained on 
and in the NOTIFY_SEND_RESPONSE and that filter READS the www-authenticate 
header!!! then IIS passes the buffer that mod_jk sends it transparently and the 
client sees the header with a single crlf.

Appending an additional crlf when there is no header seems to take care of the 
problem.

Hope this is enough detail please feel free to contact me !

all the Best
Con




.