Try using CURLOPT_COPYPOSTFIELDS option instead of CURLOPT_POSTFIELDS.
This worked for me.

Thanks
Savitha

-----Original Message-----
From: curl-library-bounces_at_cool.haxx.se [mailto:curl-library-bounces_at_cool.haxx.se] On Behalf Of Daniel Stenberg
Sent: Thursday, June 25, 2009 1:08 PM
To: libcurl development
Subject: Re: Invalid write in curl_multi_perform

On Mon, 22 Jun 2009, Hardeep Singh wrote:

> No we don't use the same handle simultaneously in multiple threads. I mean
> to say that there could be two threads running simultaneously with different
> handles. One of which is a multi handle and other one is not. The write
> error happens in curl_multi_perform, but application crashes in the
> destructor of the string that was used for setting http header options via
> curl_slist object. (for the non-multi handle).

In about 97 cases out of 100 when people reports this kind of bugs, it turns
out that their app misbehaves and overwrites some memory at some random time.
Or similar. Have you run your app with valgrind or similar?

Of course, if you can provide an example repeating this problem or can get
more data on exactly when and why it happens, then that can help too.

-- 
  / daniel.haxx.se