Submit and cookies

[msgre]

Hello Eric,
I try using twill to my tests but I am unable to successfully submit form via POST as logged user. Look at this code:

login(username="myusername", password="mypassword")
go('/myurl/')
fv(2, 'continue', '')
submit()

problem

logout()

If I print show_cookies() I get different value before and after submit. On this test I want to check, if application return the same page with form together with error messages due to mandatory form fields. But all I get is login page (because POST don't set cookies, and my code put redirection to login page).