http error

http error while uploading a .bar

Env: Bonita 6.2.0 on Tomcat 7.047, Win 7.
Bar created with studio 6.2.0
while trying to install an application thru hosted portal, I got "http error" after the .bar file is selected (on local drive) for upload.
The error message appears after a few minutes or seconds, depending on the size of the .bar, but it always happen.
The install button is never enabled.
is there any requirements for the http upload to work?
Like firewall ports open, etc.?