My b2evolution Version: 1.10.x

Hi all,
i am using Nevada, the latest version
i am on a windows server

i have the following problem:
whenever i try to leave a comment on any post, the page does not load again, instead a blank page appeares saying "Bad Request"

whenever i go back and visit this very same post, i find my comment there.

Do you have any idea how i can fix this problem??

P.S.

I have a similar problem with the LOG IN form.
whenever i log in it loads again saying that the LOG IN form has expired and that i am ALREADY logged in as "admin" for example and that i can click continue .

why does it behave in such a way?
can i fix this too????

in case you want to take a look : www.shafey.net