Unexpected Error

Hello,
I installed WordPress to my site few hours ago. And I have a few problems on it.
For example, when I click to add new plugin I get error message “An unexpected error occurred. Something may be wrong with WordPress.org or this server’s configuration. If you continue to have problems, please try the support forums.”
Also, when I try to connect jetpack with wordpress.com I get error “Jetpack could not contact WordPress.com: register_http_request_failed. This usually means something is incorrectly configured on your web host.”
I searched for this problem on support forums and couldn’t find anything that helps me. Anyone knows the solution?
Thank you