502 Bad Gateway when authorizing connection

I have a nginx 502 Bad Gateway error screen when authorizing connection betwen my WordPress.com account and Jetpack plugin.

It is interesting that when I try to authorize my account I get this error screen, then I go back to jetpack admin screen and update it. When jetpack admin screen is updated I can see that my account is already authorized.

I can not understand why does this happen. Is this a server issue or Jetpack issue.

First it happend when I updated WordPress to version 3.8.2. I also updated some plugins after that.

When I found this Bad Gateway error I deleted Jetpack plugin, manually uploaded it via FTP and then installed it. Also I returned back old WordPress 3.8.1 version from my local backup.
Never the less i still get this Bad Gateway screen.

I am a little bit worried because when I had updated website to WordPress 3.8.2 version I had this Bad Gateway message when trying to preview pending post. Going back to 3.8.1. version solved this problem.

I guess all these have something to do with recent WordPress and Jetpack updates.

What could be the reason? How can I fix it?

http://wordpress.org/plugins/jetpack/

https://wordpress.org/plugins/jetpack/