Cannot make POST with "Authorization: OAuth" headers works.

[Blaise]

Hi all,

I try to use the a POST request with the OAuth headers as follow to
post a message on my twitter:

POST /1/statuses/update.json HTTP/1.1
Host: api.twitter.com
Accept: */*
Authorization: OAuth
oauth_version="1.0",oauth_nonce="a1df9b758e16eaebe8a2208d1e210bfb",oauth_timestamp="1312861474",oauth_consumer_key="xxxxxx",oauth_token="xxxxx",oauth_signature_method="HMAC-
SHA1",oauth_signature="xxxxxx"
Content-Length: 155
Content-Type: application/x-www-form-urlencoded;
boundary=----------------------------2a715dab42e9

status=This%20is%20a%20test

I am getting the following error:
{"error":"Could not authenticate with OAuth.","request":"\/1\/statuses
\/update.json"}

My OAuth parameters are correct, posting the same request without
using the "Authorization: OAuth " header works:

POST
https://api.twitter.com/1/statuses/update.json?oauth_consumer_key=xxxx&oauth_nonce=2d6a22df9e770428993c390131e72308&oauth_signature=xxxx&oauth_signature_method=HMAC-SHA1&oauth_timestamp=1312861881&oauth_token=xxxxx&oauth_version=1.0&status=This%20is%20a%20test

So it seems that there is something specific to do when posting using
the "Authorization: OAuth" headers. Any advice?
I'm stuck on this and cannot move forward.

Thanks for replying.
Blaise.