I am running WordPress MU 2.8.4. and till today I have had no issues using the auto upgrade or auto update function of WordPress Plugins or WordPress MU Plugins until everything stopped working.

I pretty much googled for one hour and tried different solutions here and there, but nothing really worked, as the root/cause of the problem was literally at “root” level: I had to edit the /etc/hosts file on my server to reflect the correct IPs of wordpress.org

Open up the file /etc/hosts and add the following lines at the end:
You get to this file by ssh’ing into your server and typing “cd /etc/“.
On any unix server you can edit the hosts file by typing “vi hosts”
In vi, press i to insert and paste (usual command+v) the lines below.
Press ESC briefly to exit the insert-mode. Then type in the following: :wq.
The : tells vi to change into command mode, the w to write to file and the q to quit the file.
Make sure to restart the httpd service by typing service restart httpd.
Some steps may be different depending on your setup, but this should in general work!

Below the IPs and the hostnames:

72.233.56.139 wordpress.org
72.233.56.138 downloads.wordpress.org
72.233.56.139 planet.wordpress.org
74.125.47.147 blogsearch.google.com
72.233.56.139 api.wordpress.org
72.233.56.142 codex.wordpress.org

(C/P’ed from http://mu.wordpress.org/forums/topic/14891)

Of course, if the IP addresses change in future, the ones entered before will have to be changed.
This can be done by simply pinging the domains from either command line (terminal on Mac OS X or cmd on Windows), using “ping”. On Mac OS X you will want to use “ping -c 5 wordpress.org” to limit the query to five pings. If you want to stop your pinging before, just break the operation by pressing Command + C.

If you cannot use any command line tool you may want to consider using Ping.eu the cute pingu that helped me out with several network related operations in the past.

I hope this article will spare you the useless hours of Googling :)

Searched for “cannot resolve downloads.wordpress.org”
Did help:
mu.wordpress.org/forums/topic/14891

Searched for “RSS Error: WP HTTP Error: name lookup timed out”
Did not help:
WordPress › Support » Dashboard issues: RSS Error:… – wordpress.org
wordpress.org/support/topic/293871

Searched for “An Unexpected HTTP Error occurred during the API request. “
Did not help:
WordPress › Support » Plugin API HTTP Error – wordpress.org
wordpress.org/support/topic/227430
WordPress › Support » Plugin Installer Bugs – wordpress.org
wordpress.org/support/topic/215527

Searched for “An Error has occured: name lookup timed out”
Did not help:
Case Study: RSS Error: WP HTTP Error: name lookup timed out … – bestwpthemez.com
www.bestwpthemez.com/…/case-study­-rss-error-wp-http-error-name-looku
How-to Fix WP HTTP Error: name lookup timed out « Roll Over – fatlabmusic.com
fatlabmusic.com/blog/…/how-to-fix-­wp-http-error-name-lookup-timed-o…

Searched for “Download failed. name lookup timed out”
Did not help:
WordPress › Support » name lookup timed out – wordpress.org
wordpress.org/support/topic/225535
Quick ‘n Dirty solution for wordpress: Download failed.:… – minkfarmen.net
sirmc.minkfarmen.net/…/quick-n-dirty­-solution-for-wordpress-download-­…
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