curl and libcurl

Uploading a small file fails with https, resulting in an empty file instead
of a small one.

Steps to reproduce:
echo "test" > small.txt
curl -k -F file=@small.txt https://www/upload.jsp

We get the correct filename, with empty content.

The same with http works perfeclty. The same with a standard browser (IE or
firefox) works as expected.

Using a file with 60 bytes of contents works as expected.

Versions used:
* curl 7.12.1 (i386-redhat-linux-gnu) libcurl/7.12.1 OpenSSL/0.9.7a
zlib/1.2.1.2 libidn/0.5.6

* curl 7.19.0 (i386-pc-win32) libcurl/7.19.0 OpenSSL/0.9.8h zlib/1.2.3
Protocols: tftp ftp telnet dict ldap http file https ftps
Features: Largefile NTLM SSL SSPI libz

Notes:
the server certificate is invalid (self-signed)