register_http_request_failed error when trying to connect to WordPress.com

I’ve been having a problem with Jetpack slowing down load times on my site since the last upgrade, so I disabled it. I saw the help for that here: http://ww.wp.xz.cn/support/topic/jetpack-slows-down-the-site-big-server-load?replies=3
I was going to try the advice there, but when I tried to activate JP and connect it to WordPress.com, I get this error:
Jetpack could not contact WordPress.com: register_http_request_failed. This usually means something is incorrectly configured on your web host. Operation timed out after 15001 milliseconds with 0 bytes received

I am using WP with BuddyPress. I didn’t have these problems before the most recent upgrades.

http://ww.wp.xz.cn/extend/plugins/jetpack/