FORM not passing variables

can anyone tell me why the variables for this form are not being passed? I can pass the variables in a link and then it works...
I think it may have something to do with the fact that the form is posting to a secure URL?

Here is the code that does not pass the variables:
<FORM METHOD="post" ACTION=" http://post.craigslist.org/nyc/S/clt/mnh/all">
<INPUT TYPE="hidden" NAME="PostingTitle" VALUE="this is the title">
<INPUT TYPE="submit" VALUE="Post!">

This code DOES post the variables:
https://post.craigslist.org/nyc/S/for/mnh/all?PostingTitle=testing

FYI: If I post to https instead of http via the form I get "page not found". Any workaround for this?

Thanks all!