Uploading to pastebin

Plain and simple: I'm generating a list of integers from a database and I need to upload it to Pastebin.com. Here is my code:

curl_global_init(CURL_GLOBAL_ALL);
if (CURL* curl = curl_easy_init()) {
    std::ostringstream postField;
    postField << "api_user_key=" << "&" << "api_option=paste" << "&" << "api_paste_private=1" << "&";
    postField << "api_paste_name=GuidSet" << "&" << "api_paste_expire_date=10M" << "&";
    postField << "api_paste_format=text" << "&" << "api_dev_key=XXXXXXXXXXXXXXXX" << "&" << "api_paste_code=";
    for (std::set<uint32>::const_iterator itr = resultSet.begin(); itr != resultSet.end(); ++itr) {
        postField << *itr;
        if (itr != --resultSet.end())
            postField << ",";
    }

    struct MemoryStruct chunk;
    chunk.memory = (char*)malloc(1);
    chunk.size   = 1;

    curl_easy_setopt(curl, CURLOPT_URL, "http://pastebin.com/api/api_post.php");
    curl_easy_setopt(curl, CURLOPT_POST, 1);
    char* postStr = curl_easy_escape(curl, postField.str().c_str(), postField.str().length());
    printf("POST parameters: %s\n", postStr);
    curl_easy_setopt(curl, CURLOPT_POSTFIELDS, postStr);
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
    curl_easy_setopt(curl, CURLOPT_NOBODY, 0);
    curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void*)&chunk);
    curl_easy_setopt(curl, CURLOPT_USERAGENT, "TrinityCore GuidBot/1.0");

    curl_easy_perform(curl);
    curl_easy_cleanup(curl);

    self->_parentThread.sendCommand("PRIVMSG %s :%s: Finished, data available at %s",
        searchParams.targetRoom.c_str(), searchParams.actionInvoker.c_str(), chunk.memory);

    if (chunk.memory)
        free(chunk.memory);
    curl_free(postStr);
}
curl_global_cleanup();

However, when executing that code, i always get this:

* About to connect() to pastebin.com port 80 (#0)
*   Trying 72.20.36.113...
* connected
* Connected to pastebin.com (72.20.36.113) port 80 (#0)
> POST /api/api_post.php HTTP/1.1
User-Agent: TrinityCore GuidBot/1.0
Host: pastebin.com
Accept: */*
Content-Length: 609
Content-Type: application/x-www-form-urlencoded

* upload completely sent off: 609 out of 609 bytes
< HTTP/1.1 200 OK
< Server: nginx
< Date: Sun, 28 Oct 2012 11:21:33 GMT
< Content-Type: text/html
< Transfer-Encoding: chunked
< Connection: keep-alive
< Vary: Accept-Encoding
<
* Connection #0 to host pastebin.com left intact
* Closing connection #0
Bad API request, invalid api_option

Is there anything I'm obviously doing wrong ? The chunk that should be pasted has to look like "48,50,59,...etc"

Solved it myself, the problem wasnt lying in CURL, but in streaming parameters, although printf'ing stuff didnt show up any space being inserted.